Patent Publication Number: US-2007119317-A1

Title: Recording Medium Conveying Mechanism And Image Recording Device Including The Same

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a recording medium conveying mechanism that conveys a recording medium wound in a roll shape while drawing out the recording medium from one end thereof, and an image recording medium including the recording medium conveying mechanism.  
      2. Description of Related Art  
      In an image recording device such as an ink-jet printer or the like, rolled recording paper is drawn out from one end thereof, and conveyed to a recording head to be recorded. The reason for use of the rolled recording paper is to prevent occurrence of a useless margin on the recording paper when an image having an indefinite size is recorded.  
      When the rolled recording paper is used, curl is set in the recording paper because the recording paper is accommodated in a rolled state. When the recording paper is conveyed with the curl set therein, the recording paper comes into contact with each member in the device, which may induce troubles in conveying the recording paper and/or recording on the recording paper. For example, when a leading edge of the recording paper in a conveying direction where the paper is conveyed is curled upwardly, the leading edge abuts against the recording head, and paper jam may occur. Particularly when the recording paper is cut out in a predetermined length before it reaches the recording head, if the leading edge of a cut sheet formed by cutting in the conveying direction is curled, the cut sheet is floated from a recording paper support face of a belt, a platen or the like, and thus the recording paper cannot be excellently conveyed, so that the recording quality is degraded.  
      There is known a technique of correcting curl set in recording paper by providing a decurler (see JP-A-2000-226143) In this technique, the decurler includes a cylindrical member, and a peripheral surface of the cylindrical member is pressed against a surface of the recording paper so that the recording paper is curled in an opposite direction to a rolling direction of the recording paper, thereby correcting the curl set in the recording paper. After the curl set in the recording paper is corrected as described above, the recording paper is cut out by a predetermined length by a cutter and then recording is carried out on the cut sheet.  
     SUMMARY OF THE INVENTION  
      In the above technique, after the curl set in the recording paper is corrected by the decurler, the recording paper is cut by the cutter. When the operations by the cutter and the decurler are separately carried out as described above, a time loss occurs between the operations, and thus it is difficult to perform a high-speed conveyance. Therefore, high-speed print which has been recently required to recording devices such as a printer cannot be implemented.  
      An object of the present invention is to provide a recording medium conveying mechanism that can convey a rolled recording medium at a high speed even when a decurler that corrects curl set in the recording medium is provided, and an image recording device including the record medium conveying mechanism.  
      According to a first aspect of the present invention, there is provided a recording medium conveying mechanism having a conveyor that conveys a rolled recording medium while drawing out the recording medium from one end thereof, a cutter that cuts the recording medium in a predetermined length, a decurler that corrects curl set in the recording medium, and a driver that drives the cutter and the decurler so that the decurler corrects the curl in conjunction with a cutting operation by the cutter.  
      According to another aspect of the present invention, there is provided an image recording device having a recording medium conveying mechanism that conveys a rolled recording medium and a recording head that records an image on the recording medium conveyed by the recording medium conveying mechanism. The recording medium conveying mechanism includes a conveyor that conveys the rolled recording medium while drawing out the recording medium from one end thereof, a cutter that cuts the recording medium in a predetermined length, a decurler that corrects curl set in the recording medium, and a driver that drives the cutter and the decurler so that the decurler corrects the curl in conjunction with a cutting operation by the cutter.  
      According to the first and second aspects, the operation by the cutter and the operation by the decurler are carried out substantially simultaneously with each other. Therefore, the time loss occurring when these operations are carried out separately from each other can be eliminated, and the recording medium can be conveyed at high speed. In the image recording device according to the second aspect, the high-speed recording can be implemented. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other and further objects, features and advantages of the invention will appear more fully from the following description taken in connection with the accompanying drawings in which:  
       FIG. 1  is a front view showing an overall construction of an ink-jet printer according to an embodiment of the present invention;  
       FIG. 2  is a schematic diagram showing a cutter/decurler unit included in the ink-jet printer of  FIG. 1 ;  
       FIG. 3  is a schematic diagram showing a modification of a drive mechanism for the cutter/decurler unit;  
       FIG. 4A  is a schematic diagram showing a first modification of the cutter/decurler unit;  
       FIG. 4B  is a cross-sectional view taken along B-B line of  FIG. 4A ;  
       FIG. 5A  is a schematic diagram showing a second modification of the cutter/decurler unit;  
       FIG. 5B  is a cross-sectional view taken along B-B line of  FIG. 5A ;  
       FIG. 5C  is a cross-sectional view taken along C-C line of  FIG. 5A ; and  
       FIG. 6  is a cross-sectional view showing another example of an upper decurler of  FIG. 5C . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Preferred embodiments according to the present invention will be described hereunder with reference to the accompanying drawings.  
      First, an embodiment of an image recording device according to the present invention will be described. In this embodiment, a line type color ink-jet printer  1  having four ink-jet heads  2  as shown in  FIG. 1  is applied.  
      As shown in  FIG. 1 , a roll  10  achieved by winding elongated recording paper in a roll shape is accommodated in the printer  1 . The roll  10  is supported on a shaft  4  so as to be rotatable clockwise in  FIG. 1 , and one end thereof is drawn out and conveyed along a conveying direction indicated by an arrow P of  FIG. 1  while successively pinched by guide roller pairs  5 ,  6  and  7 . Each of the guide roller pairs  5 ,  6  and  7  includes a pair of cylindrical members. The length of the cylindrical members is slightly longer than the width of recording paper  10   a  which is unrolled from the roll  10 . The cylindrical members of a pair are disposed adjacently to each other, and one of the cylindrical members is rotated while the recording paper  10   a  is pinched between these cylindrical members, whereby the recording paper  10   a  is conveyed along the conveying direction P.  
      Curl is set in the recording paper  10   a  unrolled from the roll  10 . In this embodiment, the curl of the recording paper  10   a  is set so that the recording paper  10   a  is convex toward a front surface thereof, that is, a print surface.  
      A cutter/decurler unit  50  is disposed between the guide roller pairs  6  and  7 . The cutter/decurler unit  50  includes a movable blade  51  and a fixed blade  52  which are spaced from each other so as to sandwich the recording paper  10   a  therebetween, an upper decurler  61  fixed to the movable blade  51 , and a lower decurler  62  which is disposed so as to confront the upper decurler  61  and be adjacent to the fixed blade  52 . A cutting operation is carried out by the movable blade  51  and the fixed blade  52 , and a curl correcting operation is carried out by the upper decurler  61  and the lower decurler  62 .  
      The movable blade  51  has a blade inclined with respect to the horizontal direction. The movable blade  51  is disposed above a conveying passage of the recording paper  10   a  with the blade thereof facing downwardly. The fixed blade  52  has a blade inclined with respect to the horizontal direction as in the case of the movable blade  51 . The fixed blade  52  is disposed below the conveying passage of the recording paper  10   a  with the blade thereof facing upwardly.  
      The upper decurler  61  and the lower decurler  62  are respectively disposed at an upstream of the movable blade  51  and the fixed blade  52  with respect to the conveying direction P. The upper decurler  61  is formed integrally with the movable blade  51 , whereas the lower decurler  62  is not formed integrally with the fixed blade  52 . The lower decurler  62  is provided independently of the fixed blade  52  so as to be slightly spaced from the fixed blade  52 , and urged upwardly by a spring  65 . The upper decurler  61  and the lower decurler  62  are formed of elastic material such as sponge or the like.  
      The lower surface of the upper decurler  61  which faces the lower decurler  62  and the upper surface of the lower decurler  62  which faces the upper decurler  61  are curved so as to be convex in an opposite direction to a direction of the curl set in the recording paper  10   a.  In this embodiment, the direction of the curl is set so that the recording paper  10  is convex toward the front surface. Thus, the lower surface of the upper decurler  61  and the upper surface of the lower decurler  62  are curved so as to be convex toward a back surface of the paper  10 . The lower surface of the upper decurler  61  and the upper surface of the lower decurler  62  have curved shapes which are engagedly fitted to each other. As detailed later, the recording paper  10   a  is pinched by the lower surface and the upper surface.  
       FIG. 2  is a view of the cutter/decurler unit  50  which is taken from the upstream with respect to the conveying direction P. As shown in  FIG. 2 , the movable blade  51 , the fixed blade  52 , the upper decurler  61 , and the lower decurler  62  are provided so as to be elongated along a width direction of the recording paper  10   a,  and they are designed to be longer than the width of the recording paper  10   a.    
      The movable blade  51  turns in the direction of an arrow C 1  around a shaft  51   a  fixed to one end thereof. In association with this turning motion, the movable blade  51  moves relatively to the fixed blade  52 , and the upper decurler  61  moves relatively to the lower decurler  62 .  
      The movable blade  51  moves downwardly so that the blades of the movable blade  51  and the fixed blade  52  are overlapped with each other, whereby the recording paper  10   a  is cut out in the width direction. A portion of the recording paper  10   a  which is cut out by the cutting operation by the movable blade  51  and the fixed blade  52  and located at a downstream of the movable blade  51  and the fixed blade  52  with respect to the conveying direction P is conveyed as a cut sheet  10   b  to a conveying unit  30  below the head  2 . After printed, cut sheets are successively laminated and accommodated in a sheet discharge tray  20 .  
      The cutting timing of the recording paper  10   a  is controlled by a controller  90 . A sensor  17  for detecting the recording paper  10   a  is disposed at the downstream of the guide roller pair  7  with respect to the conveying direction P. The controller  90  drives a motor  80  so as to rotate the shaft  51   a  fixed to the movable blade  51  on the basis of detection information from the sensor  17  and the recording paper conveying speed based on the guide roller pairs  5 ,  6 ,  7 , etc. Thereby, the recording paper  10   a  is cut out in a predetermined length. The sensor  17  comprises an optical sensor including a light emitting element and a light receiving element, and detects the recording paper  10   a  on the basis of the difference in intensity of reflection light between the recording paper  10   a  and a sheet supply table  8   b  described later. The detection information from the sensor  17  is also used to determine, for example, the timing for starting a printing by the head  2 .  
      Substantially at the same time when the cutting operation is carried out by the overlap of the blades of the movable blade  51  and the fixed blade  52 , the upper decurler  61  is fitted to the lower decurler  62  while the recording paper  10   a  is pinched therebetween, thereby carrying out the curl correcting operation. A portion of the recording paper  10   a  where the curl is corrected is a portion serving as a leading edge in the conveying direction P when the recording paper  10   a  is cut by the movable blade  51  and the fixed blade  52 .  
      A sheet supply unit  8  is disposed at the downstream of the guide roller pair  7  with respect to the conveying direction P. The sheet supply unit  8  includes a sheet supply roller  8   a , a sheet supply table  8   b,  and a guide wall (not shown). The sheet supply roller  8   a  is disposed so that the outer peripheral surface thereof comes into contact with the surface of the recording paper  10   a  or the cut sheet  10   b.  The recording paper  10   a  and the cut sheet  10   b  will be hereinafter referred to as “sheet”. An upper surface of the sheet supply table  8   b  is disposed along the back surface of the sheet. The guide wall stands substantially vertically on the sheet supply table  8   b  and extends along the conveying direction P. In a plan view, a rotational shaft of the sheet supply roller  8   a  is not parallel to the sheet width direction but inclined by about 3° with respect to the sheet width direction.  
      When a sheet supply motor (not shown) is driven under the control of the controller  90  so that the sheet supply roller  8   a  is rotated, the sheet is conveyed along the conveying direction P while pressed against the sheet supply table  8   b . At this time, the sheet is shifted to the guide wall because the rotational shaft of the sheet supply roller  8   a  is not parallel to the sheet width direction, but inclined with respect to the sheet width direction. One end of the sheet in the width direction comes into contact with the guide wall, whereby the sheet is set to be parallel to the conveying direction P. As described above, the inclination of the sheet is corrected before the sheet is printed.  
      The conveying unit  30  is disposed at the downstream of the sheet supply unit  8  with respect to the conveying direction P. The conveying unit  30  includes two belt rollers  31 ,  32 , a loop-shaped conveying belt  33  suspended around both the rollers  31 ,  32 , and a belt guide  37  having a substantially rectangular parallelepiped shape disposed in an area surrounded by the conveying belt  33 . The belt guide  37  has substantially the same width as the conveying belt  33 , and it is brought into contact with an inner peripheral surface of an upper loop of the conveying belt  33  to support the conveying belt  33 .  
      The conveying belt  33  is formed of silicon rubber, EPDM (Ethylene Propylene Diene Monomer), urethane rubber, butyl rubber or the like, for example, and the outer peripheral surface thereof is formed of adhesive silicon rubber. Accordingly, the conveying belt  33  conveys a sheet with the sheet close contact with the outer peripheral surface of the conveying belt  33 .  
      The belt roller  31  is a driving roller, and it is rotated in a clockwise direction of  FIG. 1  by driving a conveying motor (not shown) under the control of the controller  90 . Accordingly, the conveying belt  33  runs, and the other roller  32  serving as a driven roller is also rotated.  
      A press roller  9  is disposed at the downstream of the belt roller  32  with respect to the conveying direction P and at the upstream of the head  2  with respect to the conveying direction P so as to face the belt guide  37 . The press roller  9  presses the sheet fed onto the conveying belt  33  against the conveying belt  33  before the sheet reaches the head  2 , and enables the printing to be carried out under the state that the sheet surely comes into close contact with the outer peripheral surface of the conveying belt  33 . A peeling plate (not shown) is disposed at the downstream of the head  2  with respect to the conveying direction P and before a sheet discharge tray  20 . The sheet in close contact with the conveying belt  33  is peeled from the conveying belt  33  by the peeling plate, and then accommodated in the sheet discharge tray  20 .  
      The four heads  2  are disposed adjacent to each other along the conveying direction P. Each head  2  has a head main body  2   a  at the lower end thereof, and a lower surface of the head main body  2   a  is designed as an ink ejection face  2   b  in which many openings (not shown) of a nozzle for ejecting ink are formed. The ink ejection face  2   b  is confronted to the outer peripheral surface of the conveying belt  33  through a slight gap interval. Ink of magenta, yellow, cyan and black is ejected from the ink ejection faces  2   b  of the four head main bodies  2   a,  respectively. The head main body  2   a  has a slender rectangular plane extending along a direction perpendicular to the drawing sheet of  FIG. 1 , that is, along a direction perpendicular to the conveying direction P. The head main body  2   a  has a length larger than the width of a sheet. When the sheet is moved through a space below the ink ejection faces  2   b  of the heads  2  in association with the running of the conveying belt  33  while supported on the conveying belt  33 , color ink is ejected from the respective ink ejection faces  2   b,  whereby a desired color image is recorded on the sheet.  
      As described above, according to this embodiment, the cutting operation by the movable blade  51  and the fixed blade  52  and the curl correcting operation by the upper decurler  61  and the lower decurler  62  are carried out substantially simultaneously with each other. Therefore, the time loss occurring when these operations are carried out separately from each other can be nullified, and the sheet can be conveyed at high speed. Thus, the high speed printing can be implemented.  
      A portion of the recording paper  10   a  which is subjected to the curl correction while pinched between the upper and lower decurlers  61  and  62  serves as a leading edge in the conveying direction P when recording paper  10   a  is cut by the movable blade  51  and the fixed blade  52 . When the portion of the recording paper  10   a  at the upstream of the cut portion of the recording paper  10   a  with respect to the conveying direction P, that is, the leading edge of the recording paper  10   a  in the conveying direction P is curled, the sheet is floated from the support face of the conveying belt  33  or the like, and thus the excellent conveyance cannot be performed. However, such a problem can be avoided by this embodiment.  
      In this embodiment, the movable blade  51  and the upper decurler  61  are driven through the motor  80  as a single driving source, and thus the construction can be more simplified and the cost can be more reduced as compared with a case where the movable blade  51  and the upper decurler  61  are provided with separate driving sources.  
      The simplification of the construction and the reduction of the cost can be implemented by forming the upper decurler  61  and the movable blade  51  integrally with each other.  
      The decurler of this embodiment includes the upper decurler  61  and the lower decurler  62  which are spaced from each other so as to sandwich the recording paper  10   a  therebetween. The upper and lower decurlers  61  and  62  are relatively moved and pinch the recording paper  10   a  to carry out the curl correction. The movable blade  51  and the fixed blade  52  carry out the same operation as the pinching operation of the recording paper  10   a,  and thus in the case of this construction, the cutting operation by the movable blade  51  and the fixed blade  52  and the operation by the decurler can be easily interlocked with each other.  
      The portions of the upper decurler  61  and the lower decurler  62  between which the recording paper  10   a  is pinched are curved in the opposite direction to the direction of the curl set in the recording paper  10   a.  Accordingly, as compared with a case where the portions concerned are flat, the curl correction can be more efficiently performed.  
      Both the upper decurler  61  and the lower decurler  62  are formed of elastic material such as sponge or the like, and thereby to achieve an effect that the curl correction is excellently performed without applying any inappropriate force to the recording paper  10   a.  Furthermore, the same effect can be achieved by urging the lower decurler  62  to the upper decurler  61  through the spring  65 .  
      The cutter of this embodiment includes the fixed blade  52  and the movable blade  51  that are disposed so as to extend in the width direction of the recording paper  10   a  and spaced from each other so as to sandwich the recording paper  10   a  therebetween, and the upper decurler  61  is fixed to the movable blade  51  at the upstream with respect to the conveying direction P. In this case, the upper decurler  61  is moved in conjunction with the movement of the movable blade  51 , so that the construction can be efficiently simplified, and the curl set in the leading edge in the conveying direction P of the recording paper  10   a  can be corrected immediately after the cutting operation, thereby excellently conveying the recording paper  10   a.    
      The controller  90  of the ink-jet printer  1  controls the motor  80  so that the cutting operation by the cutter and the curl correction by the decurler are carried out before the sheet reaches the head  2 . By cutting the sheet before print, the sheet is not wasted even when no-margin print is carried out, and it is unnecessary to rewind the sheet after print.  
      A drive mechanism for the cutter/decurler unit  50  is not limited to the one shown in  FIG. 2 . It may be one as shown in  FIG. 3  for example. In a modification shown in  FIG. 3 , the shaft  51   a  is not fixed to the movable blade  51 , but is fixed to a main body of the printer  1  while rotatably supporting the movable blade  51 . A cutter holder  70  is fixed to the other end of the movable blade  51 . An end face of the cutter holder  70  has a shape of arc centered about the shaft  51   a.  Teeth engageable with a gear  75  are formed on the end face of the cutter holder  70 . The gear  75  rotates on and with a shaft  75   a  that is rotatably mounted to the main body of the printer  1 . When the motor  80  is driven under control by the controller  90 , the shaft  75   a  rotates in one direction and a reverse direction. The gear  75  rotates accordingly, so that the cutter holder  70  which is engaged with the teeth of the gear  75  swings on the shaft  51   a  in the direction of an arrow C 1 . As a consequence, the movable blade  51  moves relative to the fixed blade  52 , and the upper decurler  61  moves relative to the lower decurler  62 .  
      In the modification shown in  FIG. 3 , driving force of the motor  80  is, unlike in  FIG. 2 , not transmitted to the shaft  51   a  but to the shaft  75   a  of the gear  75 . In this case, a torque required of the motor  80  is smaller than that in the construction shown in  FIG. 2 . Therefore, a small-size motor can be adopted.  
      Next, a modification of the cutter/decurler unit will be described with reference to  FIGS. 4A, 4B ,  5 A,  5 B,  5 C and  6 .  
       FIGS. 4A and 4B  show a first modification of the cutter/decurler unit. In a cutter/decurler unit  150  of this modification, the fixed blade  52  and the lower decurler  62  which are the same as the above-described embodiment are provided below the conveying passage of the recording paper  10   a.  In place of the movable blade  51  of the above-described embodiment, a circular blade  151  is provided above the conveying passage of the recording paper  10   a.    
      The circular blade  151  is provided on a movable member  151   b  so as to be rotatable around a rotational shaft  151   a  erected along the conveying direction P. The circular blade  151  is moved in the direction of an arrow C 2  in association with the movement of the movable member  151   b  in the width direction of the recording paper  10   a,  i.e., in the direction of the arrow C 2 , while clockwise rotating around the rotational shaft  151   a.  A lower part of the circular blade  151  is overlapped with the fixed blade  52  with respect to the conveying direction P. In association with the above movement, the recording paper  10   a  is successively cut from one end in the width direction thereof, i.e., from left in  FIG. 4A .  
      An upper decurler  161  is fixed to a surface of the movable member  151   b  which faces the upstream in the conveying direction P. The upper decurler  161  can be moved integrally with the movable member  151   b  and the circular blade  151  in association with the movement of the movable member  151   b  in the direction of the arrow C 2 . As shown in  FIG. 4A , the upper decurler  161  is provided at the upstream of the circular blade  151  with respect to the moving direction of the movable member  151   b , i.e., the direction of the arrow C 2 , so as to be slightly overlapped with the circular blade  151  in the conveying direction P. As in the case of the upper decurler  61  of the above-described embodiment, the upper decurler  161  is formed of elastic material such as sponge or the like, and the lower surface thereof which faces the lower decurler  62  is curved in the opposite direction to the curl direction of the recording paper  10   a.    
      According to this modification, the upper decurler  161  is moved in conjunction with the movement of the circular blade  151 , whereby the construction can be efficiently simplified as in the case of the above-described embodiment. Furthermore, the upper decurler  161  is fixed to the upstream of the circular blade  151  with respect to the moving direction of the rotational shaft  151   a,  i.e., the direction of the arrow C 2 . Thus, the curl correction can be carried out on the leading edge in the conveying direction P of the recording paper  10   a  immediately after the cutting by the circular blade  151 , so that the excellent conveyance can be performed.  
       FIGS. 5A  to  5 C show a second modification of the cutter/decurler unit. In a cutter/decurler unit  250  of this modification, the same fixed blade  52  as the above-described embodiment and a decurler  262  which is different from the lower decurler  62  of the above-described embodiment only in that the upper surface is not curved but flat are provided below the conveying passage of the recording paper  10   a.  A circular blade  251  similar to the circular blade  151  of the first modification is provided above the conveying passage of the recording paper  10   a.    
      The circular blade  251  has a rotational shaft  251   a  extending along the conveying direction P and moving along the width direction of the recording paper  10   a,  i.e., the direction of an arrow C 3 , similarly to the circular blade  151  of the first modification. As in the case of the circular blade  151  of the first embodiment, a lower part of the circular blade  251  is overlapped with the fixed blade  52  with respect to the conveying direction P, and in association with the movement described above, the recording paper  10   a  is successively cut from one end thereof in the width direction.  
      The circular blade  151  of the first embodiment is movable in only one direction from left to right in  FIG. 4A , whereas the circular blade  251  of this modification is reciprocally movable from left to right and from right to left in  FIG. 5A . After the circular blade  251  is moved from left to right, it is unnecessary to return the circular blade  251  to left again for the next cutting operation. In this case, the circular blade  251  may be temporarily stopped and then it is moved from right to left for the next cutting operation. When the circular blade  251  is moved from left to right as shown in  FIG. 5A , the circular blade  251  is clockwise rotated around the rotational shaft  251   a,  and when the circular blade  251  is moved from right to left, the circular blade  251  is counterclockwise rotated around the rotational shaft  251   a.    
      Upper decurlers  261   a  and  261   b  which are smaller than the circular blade  251  by one size are respectively provided at both sides of the circular blade  251  with respect to the width direction of the recording paper  10   a.  The upper decurler  261   a  and  261   b  are fixed to the circular blade  251  through an arm  253  fixed to the rotational shaft  251   a.  The upper decurler  261   a  and  261   b  are formed of a rigid material having little elasticity unlike the decurlers  61 ,  161 .  
      The circular blade  251  is fixed to a carriage  283  through the rotational shaft  251   a.  A guide bar  280  extending in the width direction of the recording paper  10   a  penetrates through the carriage  283  so as to be slidable, and also a part of the lower loop of a timing belt  273  suspended between pulleys  271  and  272  is fixed to the carriage  283 . When the timing belt  273  runs in association with the rotation of the pulleys  271 ,  272 , the carriage  283  fixed to the timing belt  273  is moved in the direction of the arrow C 3  while sliding along the guide bar  280 . In association with the movement of the carriage  283 , the circular blade  251  fixed to the carriage  283  is also moved.  
      Switching walls  281  and  282  are respectively fixed to the ends of the guide bar  280 . A surface of each switching wall  281 ,  282  which faces the center in the width direction of the recording paper  10   a  is inclined so that as the position on the surface is higher in the vertical direction, it is nearer to the center in the width direction of the recording paper  10   a.  Under the state shown in  FIG. 5A , the upper decurler  261   a  on the left is disposed at a lower position than the upper decurler  261   b  on the right so as to correct the curl set in the recording paper  10   a.  When the circular blade  251  is moved to the right under this state, the upper decurler  261   b  on the right is brought into contact with the switching wall  282  and further pressed downwardly while slid along the inclination surface of the switching wall  282 . In association with this motion, the upper decurler  261   a  on the left rises. Substantially at the same time when the circular blade  251  finishes the movement from left to right in  FIG. 5A , the decurler for correcting the curl is switched from the upper decurler  261   a  on the left to the upper decurler  261   b  on the right. When the circular blade  251  is moved from right to left in  FIG. 5A , the upper decurler  261   b  on the right corrects the curl set in the recording paper  10   a.  Then, substantially at the same time when the circular blade  251  finishes the movement from right to left in  FIG. 5A , the upper decurler  261   a  on the left is pressed downwardly by the switching wall  281  in the same manner as described above, whereby the decurler for correcting the curl is switched from the upper decurler  261   b  on the right to the upper decurler  261   a  on the left.  
      The peripheral surfaces of the upper decurlers  261   a,    261   b  are curved so as to be convexed outwardly (the cross-section of the upper decurler  261   a  only is shown in  FIG. 5C , however, the upper decurler  261   b  has the same cross-section). As described above, the upper decurlers  261   a  and  261   b  are formed of rigid material, and thus when the curl correction is carried out, the lower decurler  262  made of an elastic material is deformed in a concave shape by the press force of the upper decurlers  261   a,    261   b.  Accordingly, as in the case of the example of  FIG. 1 , there can be performed the curl correction which is adapted to the case where the curl of the recording paper  10   a  is set so that the recording paper  10   a  is convex to the front surface thereof.  
       FIG. 6  shows another example of the upper decurler of  FIG. 4C . An upper decurler  361   a  has a shape adapted to a case where the curl of the recording paper  10   a  is set so that the recording paper  10   a  is convex to the back surface thereof. A recess is formed on the peripheral surface of the upper decurler  361   a,  and by pressing the upper decurler  361   a  against the lower decurler  262 , the lower decurler  262  is deformed in a convex shape. Accordingly, there can be performed the curl correction adapted to a case where the curl of the recording paper  10   a  is set so that the recording paper  10   a  is convex to the back surface thereof.  
      According to this modification, the upper decurlers  261   a  and  261   b  are respectively provided to both sides of the circular blade  251  with respect to the width direction of the recording paper  10   a,  and also the switching walls  281  and  282  are provided. Accordingly, as described above, after the circular blade  251  is moved from left to right in  FIG. 5A  to cut the recording paper  10   a,  in order to carry out the next cutting operation, the circular blade  251  is moved from right to left in  FIG. 5A  without returning the circular blade  251  to left in  FIG. 5A . For example, in the first modification, the decurler  161  is provided to only one side of the circular blade  151  with respect to the width direction of the recording paper  10   a,  and also no switching mechanism like the switching walls  281  and  282  is provided. In such a case, in order to carry out the curl correction on the leading edge in the conveying direction P of the recording paper  10   a  immediately after the recording paper  10   a  is cut, it is required to fix the moving direction of the circular blade  151  at the direction of the arrow C 2  so that the decurler  161  is located at the upstream of the circular blade  151  with respect to the moving direction, i.e., the direction of the arrow C 2 , at all times. That is, after the circular blade  151  is moved along the arrow C 2  and cuts the recording paper  10   a,  the circular blade  151  must be returned to the home position on the left of  FIG. 4  again in order to carry out the next cutting operation. On the other hand, according to this modification, the operation of returning the circular blade  251  to the home position every time the cutting operation is carried out can be omitted. Therefore, a high-speed conveyance can be more effectively performed.  
      The cutter that cuts the recording paper  10   a  is not limited to those described in the above-described embodiments and modifications, and various kinds of cutters may be applied.  
      The material of the decurler is not limited to a specific one, and various shapes and constructions may be adopted for the decurler.  
      The portion of the recording paper  10   a  on which the curl is corrected by the decurler is not limited to the portion serving as the leading edge in the conveying direction P when recording paper  10   a  is cut.  
      Different driving sources may be respectively provided to the cutters such as the movable blade  51  and the decurlers.  
      It is not necessary that the upper decurler  61  and the movable blade  51  are formed integrally with each other.  
      In the above embodiments, the lower decurler  62  is urged upwardly by the spring  65 . However, the spring  65  may be omitted, and the lower decurler  62  may be fixed.  
      In  FIG. 1 , the cutter/decurler unit  50  is disposed at the upstream of the head  2  with respect to the conveying direction P, and the cutting operation by the cutter and the curl correction of the decurler are carried out before the sheet reaches the head  2 . However, the present invention is not limited to this. For example, the cutter/decurler unit  50  may be disposed at the downstream of the head  2  with respect to the conveying direction P, and the cutting operation and the curl correcting operation may be carried out after the recording paper is printed by the head  2 .  
      The image recording device of this invention is not limited to the line type ink-jet printer, and it may be applicable to a serial type ink-jet printer. Furthermore, the present invention is not limited to the printer, and it may be applied to a recording device such as a facsimile machine, a copying machine or the like. Still furthermore, the present invention is not limited to the ink-jet type recording device, and it may be applicable to various types of recording devices such as a laser type, etc.  
      The recording medium conveying mechanism of this invention maybe provided in any device in addition to the image recording device. The recording medium conveyed by the conveying mechanism is not limited to paper.  
      While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.