Patent Publication Number: US-11640128-B2

Title: Liquid discharge head, liquid discharge device, and liquid discharge apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2020-147262, filed on Sep. 2, 2020, in the Japan Patent Office, the entire disclosures of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     Aspects of the present disclosure relate to a sheet conveyor, a sheet heater, a liquid discharge apparatus, and a printer. 
     Related Art 
     A printer applies a liquid onto a print target (liquid application target) such as a sheet. The printer includes a heater to heat the sheet on which the liquid has been applied to accelerate drying of the liquid applied on the sheet conveyed by a conveyance belt. 
     SUMMARY 
     In an aspect of this disclosure, a sheet conveyor includes a conveyance belt configured to rotate to convey a sheet on which a liquid has been applied in a conveyance direction, and a guide configured to guide the sheet to the conveyance belt, a position of the guide being variable in the conveyance direction. 
     In another aspect of this disclosure, a sheet conveyor includes a conveyance belt configured to rotate to convey a sheet on which a liquid has been applied in a conveyance direction, and a downstream guide disposed downstream of the conveyance belt, the downstream guide configured to receive the sheet from the conveyance belt, a position of the downstream guide being variable in the conveyance direction. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The aforementioned and other aspects, features, and advantages of the present disclosure will be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG.  1    is a schematic cross-sectional side view of a printer as a liquid discharge apparatus according to a first embodiment of the present disclosure; 
         FIG.  2    is a plan view of a discharge unit of the printer; 
         FIG.  3    is a schematic cross-sectional side view of a sheet heater according to a first embodiment of the present disclosure; 
         FIG.  4    is a schematic cross-sectional front view of the sheet heater of  FIG.  3   ; 
         FIG.  5    is a side view of a main portion of the sheet heater according to the first embodiment illustrating a guide  560 ; 
         FIG.  6    is a schematic side view of a portion of the sheet heater illustrating a change in an interval between a first conveyance belt and a first guide due to a tension adjustment of the first conveyance belt; 
         FIG.  7    is an enlarged partial schematic side view of a tension adjustment mechanism to adjust a belt tension and a position adjustment mechanism to adjust a position of the first guide according to the first embodiment; 
         FIG.  8    is an enlarged partial schematic side view of the guide; 
         FIG.  9    is an enlarged partial schematic side view of the tension adjustment mechanism to adjust the belt tension and the position adjustment mechanism to adjust the position of the first guide according to a second embodiment of the present disclosure; 
         FIG.  10    is a schematic side view of the guide according to a third embodiment of the present disclosure; 
         FIG.  11    is a schematic side view of the guide according to a fourth embodiment of the present disclosure; and 
         FIG.  12    is a schematic side view of the first conveyance belt according to a fifth embodiment of the present disclosure. 
     
    
    
     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. 
     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 have the same function, 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. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, embodiments of the present disclosure are described below. A printer as a liquid discharge apparatus according to a first embodiment of the present disclosure is described with reference to  FIGS.  1  and  2   . 
       FIG.  1    is a schematic side view of the printer  1  according to the first embodiment. 
       FIG.  2    is a schematic plan view of a discharge unit of the printer  1 . 
     The printer  1  according to the first embodiment includes a loading unit  10  to load a sheet P into the printer  1 , a pretreatment unit  20  as an applier, a printing unit  30 , a dryer  50 , a reverse mechanism  60 , and an ejection unit  70 . 
     In the printer  1 , the pretreatment unit  20  applies, as required, a pretreatment liquid as an application liquid onto the sheet P fed (supplied) from the loading unit  10 , the printing unit  30  applies a desired liquid onto the sheet P to perform required printing. 
     After the printer  1  dries the liquid adhering to the sheet P by the dryer  50 , the printer  1  ejects the sheet P to the ejection unit  70  without printing on a back surface of the sheet P through the reverse mechanism  60 . The printer  1  may print on both sides of the sheet P via the reverse mechanism  60  after the printer  1  dries the liquid adhering to the sheet P by the dryer  50 , and the printer  1  then ejects the sheet P to the ejection unit  70 . 
     The loading unit  10  includes loading trays  11  (a lower loading tray  11 A and an upper loading tray  11 B) to accommodate a plurality of sheets P and feeding devices  12  (a feeding device  12 A and a feeding device  12 B) to separate and feed the sheets P one by one from the loading trays  11  and supplies the sheets P to the pretreatment unit  20 . 
     The pretreatment unit  20  includes, e.g., a coater  21  as a treatment-liquid application unit that applies a treatment liquid onto the sheet P to coat a printing surface of the sheet P with the treatment liquid having an effect of aggregation of ink particles to prevent bleed-through. 
     The printing unit  30  includes a drum  31  and a liquid discharge device  32 . The drum  31  is a bearer (rotating member) that bears the sheet P on a circumferential surface of the drum  31  and rotates. The liquid discharge device  32  discharges liquids toward the sheet P borne on the drum  31 . 
     The printing unit  30  includes transfer cylinders  34  and  35 . The transfer cylinder  34  receives the sheet P fed from the pretreatment unit  20  and forwards the sheet P to the drum  31 . The transfer cylinder  35  receives the sheet P conveyed by the drum  31  and forwards the sheet P to a second conveyor  41 . 
     The transfer cylinder  34  includes a sheet gripper to grip a leading end of the sheet P conveyed from the pretreatment unit  20  to the printing unit  30 . The sheet P thus gripped by the transfer cylinder  34  is conveyed as the transfer cylinder  34  rotates. The transfer cylinder  34  forwards the sheet P to the drum  31  at a position opposite (facing) the drum  31 . 
     Similarly, the drum  31  includes a sheet gripper on a surface of the drum  31 , and the leading end of the sheet P is gripped by the sheet gripper of the drum  31 . The drum  31  includes a plurality of suction holes dispersed on a surface of the drum  31 , and a suction unit generates suction airflows directed from desired suction holes of the drum  31  to an interior of the drum  31 . 
     The sheet gripper of the drum  31  grips the leading end of the sheet P forwarded from the transfer cylinder  34  to the drum  31 , and the sheet P is attracted to and borne on the drum  31  by the suction airflows by the suction device. As the drum  31  rotates, the sheet P is conveyed. 
     The liquid discharge device  32  includes discharge units  33  (discharge units  33 A to  33 D) to discharge liquids onto the sheet P as a liquid application device. For example, the discharge unit  33 A discharges a liquid of cyan (C), the discharge unit  33 B discharges a liquid of magenta (M), the discharge unit  33 C discharges a liquid of yellow (Y), and the discharge unit  33 D discharges a liquid of black (K). Further, a discharge unit may discharge a special liquid, that is, a liquid of spot color such as white, gold, or silver. 
     As illustrated in  FIG.  2   , for example, each of the discharge unit  33  includes a head module  100  including a full line head. The head module  100  includes a plurality of liquid discharge heads  101  arranged in a staggered manner on a base  103 . Each of the liquid discharge heads  101  includes a plurality of nozzle rows, and a plurality of nozzles  111  is arranged in each of the nozzle rows. Hereinafter, the “liquid discharge head  101 ” is simply referred to as a “head  101 ”. 
     The printing unit  30  controls a discharge operation of each discharge unit  33  of the liquid discharge device  32  by a drive signal corresponding to print data. When the sheet P borne on the drum  31  passes through a region facing the liquid discharge device  32 , the liquids of respective colors are discharged from the discharge units  33  toward the sheet P, and an image corresponding to the print data is formed on the sheet P. 
     The drum  31  forwards the sheet P to which a liquid is applied by the liquid discharge device  32  to the transfer cylinder  35 . The transfer cylinder  35  forwards the sheet P fed from the drum  31  to the second conveyor  41 . The sheet is conveyed from the second conveyor  41  to the dryer  50  (heater). 
     The dryer  50  serving as a dryer includes a heating device  52 . The dryer  50  heats and dries the sheet P, on which the liquid is applied, while conveying the sheet P fed from the second conveyor  41  by the first conveyor  51 . 
     The reverse mechanism  60  includes a reverse part  61  and a duplex conveyor  62 . The reverse mechanism  60  reverses the sheet P that has passed through the dryer  50  to dry a first surface of the sheet P onto which the liquid is applied when the printer  1  performs a duplex printing. The duplex conveyor  62  feeds the reversed sheet P back upstream from the transfer cylinder  34  of the printing unit  30 . The reverse part  61  reverses the sheet P by switchback manner. 
     The ejection unit  70  includes an ejection tray  71  on which a plurality of sheets P is stacked. The plurality of sheets P conveyed from the reverse mechanism  60  is sequentially stacked and held on the ejection tray  71 . 
     In the present embodiment, an example in which the sheet is a cut sheet is described. However, embodiments of the present disclosure can also be applied to an apparatus using a continuous medium (web) such as continuous paper or roll paper, an apparatus using a sheet material such as wallpaper, and the like. 
     A sheet heater  500  according to a first embodiment of the present disclosure is described with reference to  FIGS.  3  and  4   . The sheet heater  500  includes a sheet conveyor  80  to convey the sheet P according to the first embodiment of the present disclosure. 
       FIG.  3    is a schematic cross-sectional side view of the sheet heater  500  according to the first embodiment of the present disclosure. 
       FIG.  4    is a schematic cross-sectional front view of the sheet heater  500  according to the first embodiment of the present disclosure. 
     The sheet heater  500  includes a first conveyance mechanism  501 , a heating unit  502 , a second conveyance mechanism  401 , and a preheater  301 . The first conveyance mechanism  501  serves as the first conveyor  51  (see  FIG.  1   ). The heating unit  502  also serves as the heating device  52  (see  FIG.  1   ). The second conveyance mechanism  401  serves as the second conveyor  41  (see  FIG.  1   ). 
     Thus, the sheet heater  500  includes parts of the dryer  50  such as the heating device  52  and the first conveyor  51  and parts of the printing unit  30  such as the transfer cylinder  35  and the second conveyor  41 . The first conveyor  51  and the second conveyor  41  configure a sheet conveyor  80  (see  FIG.  1   ) in embodiments as described below. 
     The first conveyance mechanism  501  includes a first conveyance belt  511  that bears and conveys the sheet P. The conveyance belt  511  is an endless conveyor. The first conveyance belt  511  is an endless belt stretched between a drive roller  512  as a drive rotator and a driven roller  513  as a driven rotator. The conveyance belt  511  orbits and rotates to move the sheet P. The drive roller  512  is rotationally driven by, e.g., a drive motor  590  via a timing belt. 
     The first conveyance belt  511  is a belt that includes a plurality of openings from which air is sucked by a suction chamber  514  arranged inside the first conveyance belt  511 . The suction chamber  514  serves as a suction mechanism. The first conveyance belt  511  may be, for example, a mesh belt, a plain weave belt having a suction hole, or the like. The suction chamber  514  includes a suction blower, a fan, or the like to suck the air through the plurality of openings in the first conveyance belt  511  to attract the sheet P to the first conveyance belt  511 . The conveyor (first conveyance belt  511 ) is not limited to the conveyor that uses suction method to attract and convey the sheet P as described above. The conveyor may attract and convey the sheet P on the conveyor by, for example, an electrostatic adsorption method or a gripping method using a gripper. 
     The heating unit  502  includes a plurality of ultraviolet irradiators  521  disposed in a housing  503  along a “conveyance direction” of the sheet P as indicated by arrow in  FIG.  3   . The ultraviolet irradiators  521  irradiate the sheet P conveyed by the first conveyance belt  511  of the first conveyance mechanism  501  with ultraviolet rays to heat the sheet P. 
     The ultraviolet irradiator  521  includes granular ultraviolet light emitting diode elements  522  (UV-LED elements) arranged in a grid pattern on an irradiation surface of the ultraviolet irradiator  521 . Since the UV-LED elements  522  emit light at an identical illuminance, the ultraviolet irradiator  521  uniformly emits light along the irradiation surface as a whole. 
     As a wavelength of the ultraviolet light (UV light), a wavelength having a peak wavelength of 395 nm and a wavelength distribution having a full width at half maximum of about 15 nm is used. However, the wavelength and wavelength distribution of the ultraviolet light (UV light) is not limited the wavelength as described above and may be any other wavelength. 
     As illustrated in  FIG.  3   , the housing  503  is arranged to have a gap with the conveyance belt  511  in a vertical direction, and the gap is formed along the conveyance direction of the sheet P. As illustrated in  FIG.  4   , the housing  503  includes an extension portion  503   a  extended lower than conveyance belt  511  in a vertical (height) direction perpendicular to the conveyance direction of the sheet P. 
     The second conveyance mechanism  401  is disposed upstream from the first conveyance belt  511 . 
     The second conveyance mechanism  401  includes a second conveyance belt  411  that bears and conveys the sheet P. The second conveyance belt  411  is an endless conveyor. The second conveyance belt  411  is stretched between a drive roller  412  and a driven roller  413 . The conveyance belt  511  orbits and rotates to move the sheet P. The drive roller  412  is rotationally driven by, e.g., a drive motor  490  via a timing belt. 
     The second conveyance belt  411  is a belt that includes a plurality of openings from which air is sucked by a suction chamber  414  disposed inside the second conveyance belt  411 . The second conveyance belt  411  may be, for example, a mesh belt, a plain weave belt having a suction hole, or the like. The suction chamber  414  includes a suction blower, a fan, or the like to suck the air through the plurality of openings in the second conveyance belt  411  to attract the sheet P to the second conveyance belt  411 . The conveyor (second conveyance belt  411 ) is not limited to the conveyor that uses suction method to attract and convey the sheet P as described above. The conveyor may attract and convey the sheet P on the conveyor by, for example, an electrostatic adsorption method or a gripping method using a gripper. 
     The sheet heater  500  includes a guide  560  between the second conveyance belt  411  and the first conveyance belt  511 . The guide  560  serves as a guide to guide the sheet P from the second conveyance belt  411  to the first conveyance belt  511 . 
     The sheet heater  500  includes a preheater  301  that heats at least one of the sheet P and the transfer cylinder  35  before the sheet P, onto which the liquid has been applied, is conveyed from the transfer cylinder  35  to the second conveyance belt  411 . 
     The preheater  301  is a non-contact heater to heat the sheet P in a non-contact manner. The preheater  301  includes an air blower  311  to blow warm air toward the transfer cylinder  35 . 
     The preheater  301  dries the sheet P until the pigment contained in the liquid applied to the sheet P does not move, and the transfer cylinder  35  forwards the dried sheet P to the second conveyance belt  411  in the sheet heater  500  according to the first embodiment. 
     Since no heat source is disposed around the second conveyance belt  411 , the sheet P forwarded to the second conveyance belt  411  is conveyed in a normal temperature environment. 
     Since the temperature of the second conveyance belt  411  is reduced (lower than the temperature of the first conveyance belt  511 ), the sheet heater  500  can reduce the movement of the pigment in the liquid (ink) on the sheet P and can also reduce an occurrence of cockling of the sheet P. The movement of the pigment in the ink (liquid) occurs when the sheet P contacting a high-temperature portion of the second conveyance belt  411 . 
     Then, the guide  560  guides the sheet P conveyed from the second conveyance belt  411  to the first conveyance belt  511 . The ultraviolet irradiator  521  irradiates the sheet P conveyed by the first conveyance belt  511  with ultraviolet rays to heat the liquid (ink) on the sheet P. Thus, the liquid (ink) on the sheet P is heated by the ultraviolet irradiator  521  and dried to the final image quality. 
     The heating unit  502  is not limited to the ultraviolet irradiator  521 . The heating unit  502  may be other heating units such as an infrared irradiator or an air blower. 
     Next, a specific configuration of the guide  560  is described below in detail with reference to  FIG.  5   . 
       FIG.  5    is a side view of a main portion of the guide  560 . 
     The guide  560  includes a first guide  561  and a second guide  562 . The first guide  561  is disposed upstream of the driven roller  513  of the first conveyance belt  511  and downstream of the second conveyance belt  411 . The first guide  561  guides the sheet P to the first conveyance belt  511 . The second guide  562  is disposed upstream of the first guide  561 . The second guide  562  receives the sheet P from the second conveyance belt  411  and guides the sheet P to the first guide  561 . 
     The second guide  562  is disposed downstream of the second conveyance belt  411 . Both sides of the second guide  562  crossing the conveyance direction are fixed by side plates. The second guide  562  receives the sheet P fed from the second conveyance belt  411  and guides the sheet P to the first guide  561 . 
     The second guide  562  includes an inclined portion  562   b  and a second guide portion  562   a . The inclined portion  562   b  serves as a first guide portion and is inclined upward from an upstream end of the inclined portion  562   b  toward a downstream end of the inclined portion  562   b  in the conveyance direction. The second guide portion  562   a  is horizontally aligned and is disposed downstream of the inclined portion  562   b.    
     An upstream end of the inclined portion  562   b  of the second guide  562  is lower than a conveyance path T indicated by an imaginary line by a distance “a” as illustrated in  FIG.  5   . Thus, even if a leading end of the sheet P moves along an outer periphery of the drive roller  412 , the inclined portion  562   b  of the second guide  562  can scoop up the leading end of the sheet P. 
     The first guide  561  is disposed downstream of the second guide  562  and upstream of the first conveyance belt  511 . The first guide  561  guides the sheet P from the second guide  562  to the first conveyance belt  511 . 
     A downstream end of the second guide  562  in the conveyance direction (second guide portion  562   a ) is disposed directly (immediately) above an upstream end of the inclined portion  561   b  of the first guide  561  in the conveyance direction as indicated by a broken line “b”. Thus, the first guide  561  can smoothly receive the sheet P fed from the second guide portion  562   a  of the second guide  562 . 
     The first guide  561  receives the sheet P conveyed along the second guide  562  and guides the sheet P to the first conveyance belt  511 . The first guide  561  includes an inclined portion  561   b  and a second guide portion  561   a . The second guide portion  561   a  is also referred to as a “downstream end portion”. 
     The inclined portion  561   b  serves as a first guide portion and is inclined upward from an upstream end of the inclined portion  561   b  toward a downstream end of the inclined portion  561   b  in the conveyance direction. The second guide portion  561   a  is horizontally aligned and is disposed downstream of the inclined portion  561   b  in the conveyance direction. 
     As described above, the downstream end of the second guide portion  562   a  of the second guide  562  in the conveyance direction is disposed immediately above the upstream end of the inclined portion  561   b  of the first guide  561  in the conveyance direction as illustrated by the broken line “b” in  FIG.  5   . 
     Therefore, even if the leading end of the sheet P having passed through the second guide  562  hangs down, the sheet P can be reliably received by the inclined portion  561   b  of the first guide  561 . 
     A direction of the second guide portion  561   a  of the first guide  561  is substantially the same as a direction of a belt surface  511   a  of the first conveyance belt  511 . Thus, posture of the leading end of the sheet P becomes along the belt surface  511   a  so that the first guide  561  can prevent the sheet P from fluttering on the first conveyance belt  511  when the sheet P lands on the belt surface  511   a  of the first conveyance belt  511 . The belt surface  511   a  is also referred to as a “conveyance surface”. 
     In this way, the guide  560  can restrict an area in which the sheet P does not partially contact the belt surface  511   a  of the first conveyance belt  511 . Thus, the guide  560  can reduce waving (cockling) of the sheet P due to a difference in drying property of the liquid (ink) on the sheet P. 
     The sheet heater  500  according to the first embodiment includes the first guide  561  that is horizontally movable in a direction parallel to the belt surface  511   a  of the first conveyance belt  511 . The first guide  561  can adjust a distance (interval) between the first guide  561  and the driven roller  513  of the first conveyance mechanism  501 . The first conveyance belt  511  is wound around the drive roller  512  and the driven roller  513 . 
     Thus, the first guide  561  can appropriately adjust the distance between the first conveyance belt  511  and the first guide  561  to prevent paper jam of the sheet P. Thus, the first guide  561  can reduce occurrence of paper jam of the sheet P guided from the first guide  561  toward the first conveyance belt  511 . 
     A change in a distance between the first conveyance belt  511  and the first guide  561  according to a tension adjustment of the first conveyance belt  511  is described below with reference to  FIG.  6   . 
       FIG.  6    is an enlarged partial schematic side view of the sheet heater  500 . 
     The driven roller  513  is movable in a direction as indicated by arrow in  FIG.  6    to change the distance between the drive roller  512  and the driven roller  513  so that the driven roller  513  can adjust tension of the first conveyance belt  511  (belt tension). Here, when the circumferential length of the first conveyance belt  511  is long, a fluctuation of the distance between the drive roller  512  and the driven roller  513  due to the belt tension of the first conveyance belt  511  increases. Thus, when a belt unit is attached to a frame of the sheet heater  500 , a center position of the driven roller  513  varies. 
     The belt unit includes the first conveyance belt  511 , the drive roller  512 , the driven roller  513 , and the like to form a single body of the belt unit of the first conveyance mechanism  501 . 
     At this time, when the driven roller  513  is moved, the distance between the driven roller  513  and the first guide  561  changes, and the distance between the first conveyance belt  511  and the first guide  561  changes. 
     When the distance between the driven roller  513  and the first guide  561  increases, the sheet P may enter a gap  800  formed between the first guide  561  and the first conveyance belt  511 , and a jam occurs. 
     Conversely, when the distance between the driven roller  513  and the first guide  561  is narrow, the first conveyance belt  511  and the first guide  561  may interfere with each other during adjusting the tension of the first conveyance belt  511 . 
     Therefore, the sheet heater  500  according to the first embodiment includes the first guide  561  having an adjustable position in the conveyance direction. Thus, the position of the first guide  561  is variable in the conveyance direction. Thus, the sheet heater  500  can maintain the gap  800  between the first guide  561  and the first conveyance belt  511  at a desired distance to prevent the occurrence of the jam. 
     Next, a mechanism for adjusting the belt tension (tension adjustment mechanism) and a mechanism for adjusting a position of the first guide (position adjustment mechanism) in the first embodiment are described with reference to  FIGS.  7  and  8   . 
       FIG.  7    is an enlarged partial schematic side view of the tension adjustment mechanism and the position adjustment mechanism in the first embodiment. 
       FIG.  8    is an enlarged partial schematic side view of the sheet heater  500 . 
     The tension adjustment mechanism adjusts the belt tension of the first conveyance belt  511 . The tension adjustment mechanism includes tension plates  531  to hold both ends of an axis  513   a  of the driven roller  513 . The tension plates  531  are held so that the tension plates  531  are movable in the horizontal direction (conveyance direction) along two guide rails  532  as indicated by arrow in  FIG.  7   . The guide rails  532  are fixed to the frame  506 . 
     A screw  533  is fixed to a left end (drive roller  512  side) of the tension plate  531 . A compression coil spring  534  is interposed between a nut  535  screwed on the screw  533  and a fix portion  506   a  of the frame  506 . 
     The nut  535  is rotated to expand or contract the compression coil spring  534  to move the tension plate  531  and the driven roller  513 . Thus, the distance between the drive roller  512  and the driven roller  513  changes to adjust the belt tension of the first conveyance belt  511 . 
     The first guide  561  includes flanges  561   c  at both ends in a longitudinal direction of the first guide  561  of the driven roller  513 . The longitudinal direction of the first guide  561  is parallel to a longitudinal direction of the axis  513   a  and is also parallel to a direction perpendicular to a paper surface of  FIG.  7   . 
     The flange  561   c  includes long holes  561   d  longer in the conveyance direction indicated by arrow in  FIG.  8   . The conveyance direction is parallel to a movable direction of the driven roller  513 . Therefore, the first guide  561  is changeable and adjustable the position of the first guide  561  in the conveyance direction. 
     While the flange  561   c  of the first guide  561  faces an inner surface of the frame  506 , the screw  565  is inserted into the long hole  561   d  of the flange  561   c . Thus, the first guide  561  is fastened to the frame  506  at a predetermined position to fix the first guide  561  to the frame  506 . 
     Thus, the first guide  561  changes the position of the first guide  561  in the conveyance direction according to the position of the driven roller  513 . Thus, the first guide  561  can appropriately maintain the gap  800  between the first conveyance belt  511  and the first guide  561  so that the first guide  561  can prevent the occurrence of paper jam of the sheet P. 
     A sheet heater  500  according to a second embodiment of the present disclosure is described with reference to  FIG.  9   .  FIG.  9    is a schematic side view of the tension adjustment mechanism to adjust the belt tension and the position adjustment mechanism to adjust the position of the first guide  561  according to the second embodiment. 
     In the second embodiment, the driven roller  513  of the first conveyance belt  511  and the first guide  561  are attached to the tension plate  531  as described in the first embodiment. 
     The first guide  561  is fastened and fixed to the tension plate  531  by inserting screws  565  into holes (not limited to long holes  561   d ) in the flanges  561   c  at both ends in the longitudinal direction of the first guide  561 . The longitudinal direction of the first guide  561  is parallel to a longitudinal direction of the axis  513   a  of the driven roller  513  (see  FIG.  7   ) and is also parallel to a direction perpendicular to a paper surface of  FIG.  9   . 
     The first guide  561  is attached to the tension plate  531  at a position (attachment position) at which the distance between the first conveyance belt  511  and the first guide  561  becomes a predetermined (constant) distance. The first conveyance belt  511  is wound around the drive roller  512  and the driven roller  513 . Thus, the distance between the first guide  561  and the driven roller  513  is constant. 
     With such a configuration of the first guide  561 , the tension plate  531  is moved in the conveyance direction to adjust the belt tension of the first conveyance belt  511 . At the time of adjusting the belt tension, a positional relation between the driven roller  513  and the first guide  561  does not change since the driven roller  513  and the first guide  561  are fixed to the tension plate  531 . Accordingly, the sheet heater  500  according to the second embodiment can reduce occurrence of the paper jam of the sheet P. 
     In the sheet heater  500  according to the second embodiment, the belt surface  511   a  of the first conveyance belt  511  may be heated by heating unit  502  or by contacting the sheet P heated the heating unit  502 , and the belt surface  511   a  may thermally expand. In this case of thermal expansion of the belt surface  511   a  as well, the positional relationship between the driven roller  513  and the first guide  561  does not change. Thus, the sheet heater  500  can appropriately maintain the distance between the first conveyance belt  511  and the first guide  561 . 
     The sheet heater  500  according to a third embodiment according to the present disclosure is described with reference to  FIG.  10   . 
       FIG.  10    is a schematic side view of the guide  560  according to the third embodiment. 
     The sheet heater  500  according to the third embodiment includes the second guide  562 , a position of which is also adjustable in the conveyance direction together with the first guide  561 . 
     In the same manner as described above, the first guide  561  includes long holes  561   d  in the flanges  561   c  at both ends of the first guide  561  in the longitudinal direction of the first guide  561 . The long holes  561   d  are longer in the conveyance direction as indicated by arrow in  FIG.  10   . 
     The longitudinal direction of the first guide  561  is parallel to a direction perpendicular to a paper surface of  FIG.  10   . The first guide  561  is fixed to the frame  506  or the like by screws  565  respectively inserted through the long holes  561   d  of the first guide  561 . 
     Similarly, the second guide  562  includes long holes  562   d  in the flange  562   c  at both ends of the second guide  562  in the longitudinal direction of the second guide  562 . The long holes  562   d  are longer in the conveyance direction as indicated by arrow in  FIG.  10   . 
     The longitudinal direction of the second guide  562  is parallel to a direction perpendicular to a paper surface of  FIG.  10   . The second guide  562  is also fixed to the frame  506  or the like by screws  565  respectively inserted through the long holes  562   d  of the second guide  562 . 
     Thus, when the position of the first guide  561  is adjusted, the positional relation between the first guide  561  and the second guide  562  can also be adjusted. 
     Next, the sheet heater  500  according to a fourth embodiment of the present disclosure is described with reference to  FIG.  11   . 
       FIG.  11    is a schematic side view of the guide  560  according to the fourth embodiment. 
     The sheet heater  500  according to the fourth embodiment includes the second guide  562 , a position of which is also adjustable in the conveyance direction together with the first guide  561 . 
     The first guide  561  includes long holes  561   d  in the flanges  561   c  at both ends of the first guide  561  in the longitudinal direction of the first guide  561 . The long holes  561   d  are longer in the conveyance direction as indicated by arrow in  FIG.  11   . 
     The longitudinal direction of the first guide  561  is parallel to a direction perpendicular to the paper surface of  FIG.  11   . The first guide  561  is fixed to an intermediate frame  564  or the like by screws  565  respectively inserted through the long holes  561   d  of the first guide  561 . 
     Similarly, the second guide  562  includes long holes  562   d  in the flange  562   c  at both ends of the second guide  562  in the longitudinal direction of the second guide  562 . The long holes  562   d  are longer in the conveyance direction as indicated by arrow in  FIG.  11   . 
     The longitudinal direction of the second guide  562  is parallel to a direction perpendicular to a paper surface of  FIG.  10   . The second guide  562  is fixed to an intermediate frame  564  or the like by screws  565  respectively inserted through the long holes  562   d  of the second guide  562 . 
     Thus, the intermediate frame  564  can adjust the positional relation between the first guide  561  and the second guide  562 . 
     The intermediate frame  564  includes long holes  564   a  and is fixed to the frame  506  of the sheet heater  500  by screws  566  inserted through the long holes  564   a . The long holes  564   a  are also referred to as “frame long holes  564   a ”. The screws  566  are also referred to as “frame screws  566 ”. The long holes  564   a  (frame long holes) are longer in the conveyance direction as indicated by arrow in  FIG.  11   . 
     Thus, a position of the intermediate frame  564  is adjusted to adjust a position of the first guide  561  in the conveyance direction. Thus, the sheet heater  500  according to the fourth embodiment can reduce occurrence of the paper jam of the sheet P. 
     Next, the sheet heater  500  according to a fifth embodiment of the present disclosure is described with reference to  FIG.  12   . 
       FIG.  12    is a schematic side view of the sheet heater  500  according to the fifth embodiment of the present disclosure. 
     The sheet heater  500  according to the fifth embodiment includes the first conveyance belt  511  wound around the drive roller  512  and the driven roller  513 . The drive roller  512  is disposed upstream end (right end in  FIG.  12   ) of the first conveyance belt  511 , and the driven roller  513  is disposed downstream end (left end in  FIG.  12   ) of the first conveyance belt  511 . 
     The sheet heater  500  includes a third guide  563  disposed downstream end (left end in  FIG.  12   ) of the first conveyance belt  511 . The third guide  563  receives the sheet P conveyed from the first conveyance belt  511 . The third guide  563  is also referred to a “downstream guide”. 
     Similarly, to the first guide  561  described in each of the above-described embodiments, the third guide  563  is disposed so that a position of the third guide  563  is adjustable in the conveyance direction. 
     Thus, the third guide  563  can reduce occurrence of paper jam of the sheet P guided from the first conveyance belt  511  toward the third guide  563 . 
     In the present embodiments, a “liquid” discharged from the head is not particularly limited as long as the liquid has a viscosity and surface tension of degrees dischargeable from the head. 
     Preferably, the viscosity of the liquid is not greater than 30 mPa·s under ordinary temperature and ordinary pressure or by heating or cooling. 
     Examples of the liquid include a solution, a suspension, or an emulsion that contains, for example, 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 DNA, amino acid, protein, or calcium, or an edible material, such as a natural colorant. 
     Such a solution, a suspension, or an emulsion can be used for, e.g., inkjet ink, surface treatment solution, a liquid for forming components of electronic element or light-emitting element or a resist pattern of electronic circuit, or a material solution for three-dimensional fabrication. 
     Further, the water-based pigment ink is not limited to the above-mentioned embodiments and may contain an ultraviolet polymerization initiator and an ultraviolet polymerizable compound. 
     In this case, the water-based pigment ink preferably contains the ultraviolet polymerization initiator and the ultraviolet polymerizable, content of which does not cause or hardly cause curing due to a polymerization reaction even when the heater irradiates the water-based pigment ink with light. 
     Specifically, the content of the ultraviolet polymerization initiator in an ink composition is less than 0.1% by mass, or the content of the ultraviolet polymerizable compound in the ink composition is less than 5% by mass. 
     Such a configuration of the water-based pigment ink can reduce a running cost and obtain a printed matter having good safety. 
     The ultraviolet polymerizable compound may be a monomer or an oligomer. 
     Examples of the ultraviolet polymerizable compound include methacrylic acid. 
     Examples of an energy source to generate energy to discharge liquid include a piezoelectric actuator (a laminated piezoelectric element or a thin-film piezoelectric element), a thermal actuator that employs a thermoelectric conversion element, such as a heating resistor, and an electrostatic actuator including a diaphragm and opposed electrodes. 
     Examples of the “liquid discharge apparatus” include, not only apparatuses capable of discharging liquid to materials onto which liquid can adhere, but also apparatuses to discharge a liquid toward gas or into a liquid. 
     The “liquid discharge apparatus” may include devices to feed, convey, and eject the material on which liquid can adhere. 
     The liquid discharge apparatus may further include a pretreatment apparatus to coat a treatment liquid onto the material, and a post-treatment apparatus to coat a treatment liquid onto the material, onto which the liquid has been discharged. 
     The “liquid discharge apparatus” may be, for example, an image forming apparatus to form an image on a sheet by discharging ink. 
     The “liquid discharge apparatus” is not limited to an apparatus to discharge liquid to visualize meaningful images, such as letters or figures. 
     For example, the “liquid discharge apparatus” may be an apparatus to form arbitrary images, such as arbitrary patterns, or fabricate three-dimensional images. The above-described term “material on which liquid can adhere” represents a material on which liquid is at least temporarily adhered, a material on which liquid is adhered and fixed, or a material into which liquid is adhered to permeate. 
     Examples of the “material on which liquid can adhere” include recording media such as a paper sheet, recording paper, and a recording sheet of paper, film, and cloth, electronic components such as an electronic substrate and a piezoelectric element, and media such as a powder layer, an organ model, and a testing cell. 
     The “material onto which liquid can adhere” includes any material on which liquid adheres unless particularly limited. 
     Examples of the “material to which liquid can adhere” include any materials to which liquid can adhere even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramic. 
     The “liquid discharge apparatus” may be an apparatus to relatively move the head and a material on which liquid can adhere. 
     However, the liquid discharge apparatus is not limited to such an apparatus. 
     For example, the liquid discharge apparatus may be a serial head apparatus that moves the head or a line head apparatus that does not move the head. 
     Examples of the “liquid discharge apparatus” further include a treatment liquid coating apparatus to discharge a treatment liquid to a sheet to coat the treatment liquid on a sheet surface to reform the sheet surface, and an injection granulation apparatus in which a composition liquid including raw materials dispersed in a solution is injected through nozzles to granulate fine particles of the raw materials. 
     The terms “image formation”, “recording”, “printing”, “image printing”, and “fabricating” used in the present embodiments may be used synonymously with each other. 
     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 is 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.