Abstract:
The invention teaches a printer that maintains a gap, between a carrier belt and a printing head that extends for a long distance in a delivery direction of the carrier belt, uniform along the delivery direction, and increases or decreases the uniform gap along the delivery direction. The carrier belt shifts upwards or downwards by a same distance at both ends. The printer includes a printing head, a pair of rollers, a carrier belt, and a moving mechanism. The printing head prints characters or images on a sheet, and is typically an ink jet head. The carrier belt is wound around the pair of rollers. The carrier belt sends the sheet to a printing position opposing the printing head, and sends the printed sheet from the printing position. The moving mechanism includes a mechanism for shifting one of the rollers and a mechanism for shifting the other of the rollers. The rollers are shifted by the same amount.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority to Japanese Patent Application No. 2004-091062, filed on Mar. 26, 2004, the contents of which are hereby incorporated by reference into the present application. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a printer for printing on a sheet. 
   2. Description of the Related Art 
   Ordinal printer is provided with a printing head for printing on a sheet of paper or the like, and with a carrier device for delivering the sheet. Ordinal carrier device is provided with a carrier belt wound between a pair of rollers. Using the carrier belt; the sheet of paper or the like is delivered to a printing position opposing the printing head, and is delivered from the printing position. 
   In order to print sheets with differing thicknesses, a type of printer has been developed that has a device allowing the adjustment of a gap between the carrier belt and the printing head in the printing position. 
   For example, a printer disclosed in Japanese Laid Open Patent Application Publication 2003-94744 is provided with a carrier belt unit. The carrier belt unit has a carrier belt wound between a driving roller and a driven roller. The carrier belt unit can be swung around a rotary shaft of the driving roller. The gap between the printing head and the carrier belt is increased or decreased by swinging the carrier belt unit around the rotary shaft of the driving roller. 
   In the conventional printer, the gap between the printing head and the carrier belt is adjusted by swinging the carrier belt unit around the rotary shaft (the rotary shaft of the driving rotor). If the printing head extends for a short distance along a delivery direction of the carrier belt (hereafter shortened to delivery direction), there is no particular problem in adjusting the gap between the printing head and the carrier belt by means of swinging the carrier belt unit. 
   However, if the printing head extends for a long distance in the delivery direction, this method of adjusting the gap by swinging the carrier belt unit is problematic. In a case of a printer in which a plurality of printing heads is aligned in the delivery direction, the actual distance along which the printing heads extend is long, and the problem of adjusting the gap becomes quite apparent. 
   When the printing head or heads extend for a long distance in the delivery direction and the gap between the printing head and the carrier belt is adjusted by swinging the carrier belt unit, a portion of the gap at a predetermined distance from the center of swinging can be adjusted to a determined value. However, the gap cannot be adjusted to the determined value at locations which do not have the same distance relationship with respect to the center of swinging. In the conventional printer, the carrier belt unit cannot be moved in a parallel manner, and consequently the gap cannot be maintained uniform when the printing head or heads extend for a long distance in the delivery direction. 
   In a color ink jet printer, for example, four ink jet heads are aligned in the delivery direction. A technique is required for adjusting the carrier belt position so that the gap between the carrier belt and each of the ink jet heads is maintained uniform, and this uniform gap can be increased or reduced. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention proposes a printer that maintains the gap, between the carrier belt and the printing head that extends for a long distance in the delivery direction of the carrier belt, uniform along the delivery direction, and increases or decreases the uniform gap along the delivery direction. The carrier belt shift upwards or downwards by a same distance at both ends. 
   The carrier belt needs not move in a parallel manner while a gap adjusting mechanism (or a moving mechanism) is operating. If the carrier belt is shifted into a parallel position from a starting position when the gap adjusting mechanism completes operation, the gap between the carrier belt and the ink jet head can be maintained uniform along the delivery direction. 
   A printer of the present invention comprises a printing head, a pair of rollers, a carrier belt, and a moving mechanism. The printing head prints characters or images on a sheet opposing the printing head, and is typically an ink jet head, but could also be a thermal printing head or a dot printing head. The carrier belt is wound around the pair of rollers. The carrier belt sends the sheet to a printing position opposing the printing head, the sheet is printed at the printing position, and the carrier belt sends the printed sheet from the printing position. The moving mechanism shifts the pair of rollers by the same amount in a direction orthogonal to the delivery direction of the carrier belt. In the present specification, this process of shifting the pair of rollers is termed ‘changing the height’ of the rollers. The moving mechanism may not only change the height of the rollers, but may simultaneously also move the rollers in the delivery direction of the carrier belt. As long as the moving mechanism shifts or moves the rollers in the direction orthogonal to the delivery direction of the carrier belt (that is, it changes the height of the rollers), the moving mechanism may simultaneously shift or move the carrier belt in the delivery direction. The moving mechanism changes the height of the pair of rollers by the same distance before and after the operation of the moving mechanism. It is not required to maintain the pair of rollers at the same height as always. Naturally, it is possible that the height of the rollers is maintained at the same height at every instance, and this is the preferred option. 
   By providing the moving mechanism, it is possible to increase or decrease the gap between the printing head and the carrier belt so that the gap corresponds to the printing quality of the sheet, or corresponds to a change in the thickness of the sheet that is to be printed. Moreover, the gap between the printing head and the carrier belt can be increased or decreased so as to be uniform along the delivery direction, with respect to the printing head that extends for the long distance in the delivery direction. 
   The sheet can constantly be maintained parallel to the printing head face, and printing quality can thus be improved. Furthermore, the sheet can be delivered smoothly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of essential parts of an embodiment of an ink jet printer of the present invention.  FIG. 1  shows a state where a gap (g 1 ) is narrow. 
       FIG. 2  is a side view of essential parts of the embodiment of the ink jet printer of the present invention.  FIG. 2  shows a state where the gap (g 2 ) is wide. 
       FIG. 3  shows a configuration of a moving mechanism. 
       FIG. 4  shows essential parts of a driving system of a driving roller and of the moving mechanism at a driving side. 
       FIG. 5  shows a side view of essential parts of  FIG. 4 . 
       FIGS. 6(   a ) and ( b ) show an operation of the driving system of the driving roller and the driving side moving mechanism.  FIG. 6(   a ) shows the operation while the driving roller is rotating, and  FIG. 6(   b ) shows the operation while the gap is being adjusted. 
       FIGS. 7(   a ) and ( b ) schematically show essential parts of a driven side moving mechanism.  FIG. 7  (a) shows a state where a second cam member has been raised, and  FIG. 7(   b ) shows a state where the second cam member has been lowered. 
       FIG. 8  shows a cam shaft and a cam shaft supporting member. 
       FIGS. 9(   a ) and ( b ) show an operation of the cam shaft and the cam shaft supporting member while adjusting a degree of parallelization.  FIG. 9(   a ) shows a state where the cam shaft has been raised, and  FIG. 9(   b ) shows a state where the cam shaft has been lowered. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Preferred Embodiments to Practice the Invention 
   A preferred embodiment to practice the present invention will now be described. In the present embodiment, the present invention has been applied to a color ink jet printer. However, the present invention can also be applied to other types of printers. 
   An ink jet printer  1  shown in  FIG. 1  is provided with ink jet heads  2  ( 2 K,  2 ,  2 C, and  2 Y) that discharge four colors of ink: black, magenta, cyan and yellow. The ink jet printer  1  is further provided with a carrier unit  3  that carries a sheet of paper below the ink jet heads  2  from a right side of these ink jet heads  2  to a left side thereof. The carrier unit  3  utilizes a carrier belt  13  to deliver the paper. The ink jet printer  1  is provided with a main chassis  30  (not shown in  FIG. 1 , but shown in  FIG. 4 ) and a belt chassis  10 . The ink jet heads  2  are fixed to the main chassis  30 . The carrier unit  3  is assembled in the belt chassis  10 . The belt chassis  10  can be raised or lowered in a parallel manner with respect to the main chassis  30 .  FIG. 1  shows a state in which the belt chassis  10  has been raised in a parallel manner with respect to the main chassis  30 , and in which a gap g 1  between the ink jet heads  2  and the carrier belt  13  has been adjusted so as to be narrow.  FIG. 2  shows a state in which the belt chassis  10  has been lowered in a parallel manner with respect to the main chassis  30 , and in which a gap g 2  between the ink jet heads  2  and the carrier belt  13  has been adjusted so as to be wide. The belt chassis  10  can be swung, with respect to the main chassis  30 , from the angle shown by the solid line in  FIG. 1  to the angle shown by the dashed line in  FIG. 1 . The ink jet printer  1  is provided with a parallel adjusting mechanism for adjusting the angle of the belt chassis  10  with respect to the main chassis  30  such that, when the belt chassis  10  is at the angle shown by the solid line in  FIG. 1 , the gap between the ink jet heads  2  and the carrier belt  13  is uniform with respect to the four ink jet heads  2  ( 2 K,  2 M,  2 C, and  2 Y). 
   As shown in  FIG. 1 , the inkjet printer  1  is provided with a total of eight line type inkjet heads  2 . The eight line type ink jet heads  2  are fixed to the main chassis  30  (not shown in  FIG. 1 , but shown in  FIG. 4 ). Two ink jet heads  2 K discharge black ink, two ink jet heads  2 M discharge magenta ink, two ink jet heads  2 C discharge cyan ink, and two ink jet heads  2 Y discharge yellow ink. The eight ink jet heads  2  are aligned in a left-right direction of  FIG. 1  (the direction of delivery of the paper). 
   Each of the two ink jet heads  2 K,  2 M,  2 C, and  2 Y that discharge identically colored ink are adjacent in the direction of delivery of the paper. Each ink jet head  2  extends in a direction orthogonal to the page of  FIG. 1 , and extends for a length equivalent to approximately half the width of the paper. Both ink jet heads that discharge identically colored ink are disposed in locations having displacement therebetween in a direction orthogonal to the page of  FIG. 1 . Viewed from a direction orthogonal to the paper, both ink jet heads  2  that discharge identically colored ink are disposed such that end parts thereof overlap. As a result, the entire width of the paper passing below the ink jet heads  2  can be printed at the same time by using both of the ink jet heads  2  that discharge identically colored ink. The two ink jet heads  2  that discharge identically colored ink have no space therebetween along the width of the paper which would cause a blank area in the printing. 
   An ink discharging face  2   a  is formed at a lower face of each of ink jet heads  2 . A plurality of nozzles (not shown) is formed in each of the ink discharging faces  2   a . Ink is discharged from each nozzle. The paper passing below the ink discharging faces  2   a  is printed by discharging ink from the nozzles. The paper is in a printing position when facing or opposing the ink discharging faces  2   a.    
   The carrier unit  3  is assembled in the belt chassis  10 . The belt chassis  10  has a pair of plates disposed in an orthogonal manner with respect to the page of  FIG. 1 . Driving roller  11  is provided at a left side of the belt chassis  10  between the pair of plates for forming the belt chassis  10 . The driving roller  11  is supported by the belt chassis  10  such that the driving roller  11  can rotate freely with respect to the belt chassis  10 . Driven roller  12  is provided at a right side of the belt chassis  10  between the pair of plates for forming the belt chassis  10 . The driven roller  12  is supported by the belt chassis  10  such that the driven roller  12  can rotate freely with respect to the belt chassis  10 . The driving roller  11  and the driven roller  12  extend between the pair of plats for forming the belt chassis  10 . 
   A continuous or endless carrier belt  13  is wound across the driving roller  11  and the driven roller  12 . A carrier belt receiving unit  14  supports the carrier belt  13  from below. The carrier belt  13  is mounted on an upper face of the carrier belt receiving unit  14 , and the carrier belt receiving unit  14  prevents the carrier belt  13  from bending downwards. The carrier belt receiving unit  14  is fixed to the belt chassis  10 . The belt chassis  10  is pushed upwards via the carrier belt receiving unit  14  by compression springs  25  (see  FIG. 1 ). Lower ends of the compression springs  25  are supported by a cam receiving member  32 , whose height with respect to the main chassis  30  can be fixed. The structure between the belt chassis  10 , the cam receiving member  32 , the main chassis  30  and the compression springs  25  will be described later. 
   First, a mechanism to deliver the carrier belt  13  will be described As shown in  FIGS. 3 ,  4 , and  5 , a rotary shaft  11   a  of the driving roller  11  is supported such that it can be rotated with respect to the belt chassis  10  by means of a first cam member  43  (to be described). As shown in  FIG. 4 , the first cam member  43  has two cylindrical portions  43   a ,  43   c  and has a central hole  43   b . The cylindrical portion  43   a  is supported by the belt chassis  10  and the cylindrical portions  43   c  is supported by the main chassis  10 . The center of the cylindrical portions  43   a  is offset from the center of the cylindrical portions  43   c  by a distance d 1 . The rotary shaft  11   a  of the driving roller  11  is inserted into the central hole  43   b . The central hole  43   b  is located at the center of the cylindrical portion  43   a.    
   A pulley  21  is fixed to an end of the rotary shaft  11   a  of the driving roller  11 . As shown in  FIG. 3 , a pulley  24   a  is fixed to a rotary shaft of a stepping motor  24  used for driving. A carrier belt  22  is wound across the pulleys  21  and  24   a . A pulley  20  applies tension to the carrier belt  22 . The stepping motor  24  used for driving is fixed to the main chassis  30 . When the stepping motor  24  rotates, the driving roller  11  rotates, the carrier belt  13  is delivered, and the paper mounted on the carrier belt  13  is delivered towards the left relative to the left-right direction of  FIG. 1 . The driven roller  12  rotates following the delivery of the carrier belt  13 . 
   The paper is delivered from right to left relative to  FIG. 1  through a space (a gap) between the ink discharging faces  2   a  of the ink jet heads  2  and the carrier belt  13 . The ink jet printer  1  is capable of printing on sheets of paper of varying thickness, such as plain paper, photographic paper, thick paper or envelopes, etc. It is preferred that there is a short distance from the ink discharging faces  2   a  to a surface of the paper when the paper is thin, so as to increase the accuracy of impact of the ink discharged from the nozzles. This is also the case for printing high quality images on photographic paper, etc. However, for printing plain paper or the like, there is no need for the gap to be narrow when particularly high quality printing is not required. Conversely, it is difficult to deliver the paper in a stable manner if the gap between the ink discharging faces  2   a  and the carrier belt  13  is too narrow. In particular, the paper can readily become jammed when comparatively thick paper such as envelopes, etc. is used. 
   To deal with this, the ink jet printer  1  is provided with a moving mechanism  40  for adjusting the gap between the ink discharging faces  2   a  of the ink jet heads  2  and the carrier belt  13 . 
   The moving mechanism  40  is provided with a driving side moving mechanism  41  and a driven side moving mechanism  42 . The driving side moving mechanism  41  raises or lowers the driving roller  11  with respect to the main chassis  30 . The driven side moving mechanism  42  raises or lowers a portion of the belt chassis  10  at the side of the driven roller  12  (the portion at the right side of  FIG. 1 ) with respect to the main chassis  30 . 
   The ink jet heads  2  are fixed to the main chassis  30 . Consequently, the gap between the ink discharging faces  2   a  of the ink jet heads  2  and the carrier belt  13  is adjusted when the driving roller  11  and the belt chassis  10  at the side of the driven roller  12  are raised or lowered with respect to the main chassis  30 . 
   The driving side moving mechanism  41  and the driven side moving mechanism  42  are synchronized, and raise or lower the belt chassis  10  with the same timing and to the same extent. The belt chassis  10  is raised or lowered in a parallel manner, with respect to the main chassis  30 , by operating the driving side moving mechanism  41  and the driven side moving mechanism  42  in synchrony. 
   The driving side moving mechanism  41  will now be described. The driving side moving mechanism  41  raises or lowers the driving roller  11  with respect to the main chassis  30 . A left end, relative to  FIG. 1 , of the belt chassis  10  is raised or lowered with respect to the main chassis  30  when the driving roller  11  is raised or lowered with respect to the main chassis  30 . 
   As shown in  FIGS. 3 to 5 , the driving side moving mechanism  41  has the first cam member  43  and the driving motor  24  that rote the first cam member  43 . The driving motor  24  is also used to rotate the driving roller  11  and thus deliver the carrier belt  13 . 
   As shown in  FIG. 4 , the first cam member  43  is formed from two overlapping cylindrical portions  43   a  and  43   c , and the centers of the two cylindrical portions  43   a  and  43   c  are mutually offset by a distance d 1 . A hole  43   b  is formed at a center of the first cylindrical portion  43   a , and passes through the second cylindrical portion  43   c  at a location offset from its center by the distance d 1 . The rotary shaft  11   a  of the driving roller  11  passes through the hole  43   b.    
   The first cylindrical portion  43   a  is supported such that it can be rotated with respect to the belt chassis  10 , and the second cylindrical portion  43   c  is supported such that it can be rotated with respect to the main chassis  30 . As shown in  FIGS. 4 and 5 , cogs  43   d  are formed at an outer periphery of the cylindrical portion  43   c  of the first cam member  43 . 
   A gear  34  is fixed to the rotary shaft of the driving motor  24 . A sun gear  35  engages with the gear  34 . A planet gear  36  engages with the sun gear  35 . The planet gear  36  is supported, such that it can rotate, by a gear arm  37 . The gear arm  37  can rotate with the rotational center of the sun gear  35  as its center. The planet gear  36  rotates while revolving around the sun gear  35 . 
   As shown in  FIG. 6(   b ), when the gear arm  37  rotates in an counterclockwise direction, the planet gear  36  engages with the cogs  43   d  at the outer periphery of the cylindrical portion  43   c  of the first cam member  43  (this will be described in detail later). Consequently, when the motor  24  rotates, the cylindrical portion  43   c  of the first cam member  43  rotates with respect to the main chassis  30 . As described above, the rotational center of the driving roller  11  is offset by the distance d 1  from the rotational center of the cylindrical portion  43   c  of the first cam member  43 , with respect to the main chassis  30 . When the cylindrical portion  43   c  of the first cam member  43  rotates with respect to the main chassis  30 , the rotational center of the driving roller  11  moves along a circle having the radius d 1  with respect to the main chassis  30 . 
   By this means, the rotational center of the driving roller  11  can be raised and lowered with respect to the main chassis  30  between a position raised by the distance d 1  and a position lowered by the distance d 1 .  FIG. 1  and  FIG. 4  show a state in which the rotational center of the driving roller  11  is in the position raised by the distance d 1  with respect to the main chassis  30 , and in which the gap g 1  between the ink jet heads  2  and the carrier belt  13  has been adjusted so as to be narrow.  FIG. 2  shows a state in which the rotational center of the driving roller  11  is in the position lowered by the distance d 1  with respect to the main chassis  30 , and in which the gap g 2  between the ink jet heads  2  and the carrier belt  13  has been adjusted so as to be wide. 
   The rotational center of the driving roller  11  does not just move upwards and downwards, but also moves in a horizontal direction. The driven side moving mechanism  42  (to be described) allows horizontal movement of the belt chassis  10 . There is no problem if the driving roller  11  is also moving in a horizontal direction. 
   The driving side moving mechanism  41  is formed at both endes of the driving roller  11 , and is a configuration to raise or lower the driving roller  11  such that both ends thereof move in synchrony, with the same timing and to the same extent. Next, the mechanism for achieving this will be described. 
   The driving side moving mechanism  41  at the further side relative to the plane of the page of  FIG. 1  is also provided with a first cam member  43 , and is located with the same relationship as in  FIG. 4  with respect to the main chassis  30 , the belt chassis  10 , and the driving roller  11 . This differs only in that left and right are the reverse of  FIG. 4 . 
   A gear  44  engages with the cogs  43   d  formed at the outer periphery of the cylindrical portion  43   c  of the first cam member  43 . The gear  44  at the further side, and a gear  44  at a closer side, relative to the plane of the page of  FIG. 1 , join with a shaft member  45 . Since the gears  44  and the shaft member  45  are fixed, the rotation of the gear  44  at the further side and the gear  44  at the closer side is synchronized. As a result, the first cam member  43  at the further side relative to the plane of the page of  FIG. 1 , and the first cam member  43  at the closer side, rotate with the same timing and to the same extent. The end of the driving roller  11  at the further side, and the end of the driving roller  11  at the closer side are consequently raised or lowered with the same timing and to the same extent. 
   In the present embodiment, one single driving motor  24  functions as a motor that rotates the driving roller  11  and thus delivers the paper, and as a motor that rotates the first cam member  43  and raises or lowers the driving roller  11 . The number of motors is reduced, and consequently the cost of manufacturing the ink jet printer  1  can be reduced. Below, a mechanism is described whereby the driving motor  24  is used to separately drive the driving roller  11  and the first cam member  43 . 
   As shown in  FIGS. 4 and 5 , the driving motor  24  and the driving roller  11  are linked by the carrier belt  22 . In the case where paper is to be delivered, the driving motor  24  rotates in the counterclockwise direction of  FIG. 5 . This rotates the driving roller  11  in the counterclockwise direction, and the upper side of the carrier belt  13  shown in  FIG. 1  is delivered from right to left. The paper is delivered from right to left. 
   When the driving motor  24  rotates in the counterclockwise direction of  FIG. 5 , the sun gear  35  rotates in a clockwise direction, and the gear arm  37  rotates in the clockwise direction. The planet gear  36  separates from the first cam member  43 . Consequently the first cam member  43  does not rotate even if the driving motor  24  is rotating so as to deliver the paper, and the driving roller  11  is not raised or lowered. 
   This state is shown in  FIG. 6(   a ). When an output pulley  24   a  of the driving motor rotates in the counterclockwise direction of  FIG. 6 , driving force of the driving motor  24  is transmitted to the driving roller  11  via the carrier belt  22 , and the driving roller  11  is thus driven to rotate. By contrast, the planet gear  36  moves in a clockwise direction along the outer periphery of the sun gear  35 , the planet gear  36  disengages from the first cam member  43 , and the driving force of the driving motor  24  is not transmitted to the first cam member  43 , so that the first cam member  43  is not rotated. 
   When the planet gear  36  has moved by a certain extent along the outer periphery of the sun gear  35 , an end of the gear arm  37  makes contact with a stopper  38 , and this prevents the planet gear  36  from further approaching the gear  34 . This prevents interference between the planet gear  36  and the gear  34  when the driving roller  11  is rotating (while delivering the paper). 
   In the case where the driving roller  11  is raised or lowered, the driving motor  24  is rotated in the clockwise direction of  FIG. 5 . When the driving motor  24  is rotated in the clockwise direction of  FIG. 5 , the sun gear  35  rotates in the counterclockwise direction, the gear arm  37  rotates in the counterclockwise direction, and the planet gear  36  engages with the first cam member  43 . As a result, the first cam member  43  is rotated by the driving motor  24 , and the rotary shaft  11   a  of the driving roller  11  moves upwards or downwards. In this case, the driving roller  11  rotates in the clockwise direction, and the upper side of the carrier belt  13  is delivered from left to right. The paper is not present when the driving roller  11  is raised or lowered, and consequently it is not a problem that the carrier belt  13  is rotating in the reverse direction. 
   This state is shown in  FIG. 6(   b ). When the output pulley  24   a  of the driving motor rotates in the clockwise direction of  FIG. 6 , the planet gear  36  moves in the counterclockwise direction along the outer periphery of the sun gear  35 , and the planet gear  36  engages with the first cam member  43 . As a result, the driving force of the driving motor  24  is transmitted to the first cam member  43  via the gear  34 , the sun gear  35 , and the planet gear  36 . Thereupon the first cam member  43  rotates, and the rotary shaft  11   a  of the driving roller  11  moves upwards or downwards. 
   The first cam member  43  is capable of rotating with respect to the rotary shaft  11   a  of the driving roller  11 . Consequently, the first cam member  43  should not rotate even when the driving roller  11  is rotating. However, as shown in  FIG. 4 , the pulley  21  linked with the driving roller  11  is very close to one side of the first cam member  43 . There is consequently a risk that, when the driving roller  11  is rotating so as to deliver paper, friction with the pulley  21  may drive the first cam member  43  to rotate. If the first cam member  43  is driven to rotate, the height of the driving roller  11  will be changed. 
   To deal with this, the driving side moving mechanism  41  has a configuration for preventing the rotation of the first cam member  43  when the driving roller  11  is being driven to rotate by the driving motor  24 . A specific description of this configuration is given below. 
   As described above, the gears  44  engage with the pair of first cam members  43  so as to cause the first cam members  43  to rotate in a synchronized manner. A protruding part  44   a  that protrudes inwards is formed at a portion of an inner face side (the left side in  FIG. 4 ) of the gear  44 . The main chassis  30  supports the shaft member  45 , via a shaft supporting member  46 , such that the shaft member  45  can rotate. The shaft supporting member  46  is fixed to the main chassis  30 . Concave members  46   a  and  46   b  are formed in the shaft supporting member  46  at locations having point symmetry with respect to the shaft member  45 , and the protruding part  44   a  can engage with these concave members  46   a  and  46   b . Further, the shaft member  45  and the gear  44  are energized to the left, relative to  FIG. 4 , by a coiled spring  47 . This locking structure is provided only at the side shown in  FIG. 4 . 
   When the rotary shaft  11   a  of the driving roller  11  is located in a raised state with respect to the main chassis  30  (in a state where the gap g 1  is narrow), as shown in  FIG. 1 , the protruding part  44   a  is also in a raised position. The gear  44  is attracted towards the main chassis  30  by the energizing force of the coiled spring  47 , and consequently the protruding part  44   a  engages with the upper concave member  46   a , as shown in  FIG. 4 . 
   By contrast, when the rotary shaft  1   a  of the driving roller  11  is located in a lowered state with respect to the main chassis  30  (in a state where the gap g 2  is wide), the protruding part  44   a  is also in a lowered position. In this case, the protruding part  44   a  engages with the lower concave member  46   b.    
   The gear  44  cannot easily rotate when the protruding part  44   a  is engaged with the upper concave member  46   a  or the lower concave member  46   b . Consequently, it is also difficult for the first cam member  43  to rotate. The protruding part  44   a  of the gear  44  engaging with the first cam member  43 , and the concave members  46   a  and  46   b  fixed to the main chassis  30 , function as a restraining mechanism. Frictional force with the pulley  21  is thus prevented from causing the rotation of the first cam member  43  when the driving roller  11  is rotating. 
   Moreover, the energizing force of the coiled spring  47  has a strength such that the engagement of the protruding part  44   a  and the concave members  46   a  and  46   b  is not easily released due to the frictional force between the first cam member  43  and the pulley  21 . Moreover, the energizing force of the coiled spring  47  is set to a strength such that, when the first cam member  43  is being rotated, rotational resistance of the first cam member  43  does not become too great—this rotational resistance being caused by the engagement of the protruding part  44   a  and the concave members  46   a  and  46   b.    
   As shown in  FIG. 5 , a notch-shaped detected part  44   b  is formed in the gear  44  that engages with the first cam member  43 . By detecting the detected part  44   b  by using, for example, an optical sensor  48 , it is possible to detect a reference position of the first cam member  43 , i.e., a reference position of the rotary shaft  11   a  of the driving roller  11 . Further, the number of driving steps of the driving motor  24  can be amended using the reference position detected by the sensor  48 , such that it is possible to cause the first cam member  43  to rotate a determined angle from the reference position, so that the height at which the rotary shaft  11   a  of the driving roller  11  is located (the gap at side of the driving roller  11 ) can be adjusted. 
   Changes in the height of the driving roller  11  can be regulated at multiple stages by increasing the number of concave members  46  that engage with the protruding part  44   a.    
   Next, the driven side moving mechanism  42  will be described. 
   As shown in  FIG. 3 , the driven side moving mechanism  42  has a cam shaft  50  and a second cam member  51 . The main chassis  30  supports the cam shaft  50  such that the cam shaft  50  can rotate with respect to the main chassis  30 , at an upwards side (the ink jet head  2  side) from the carrier belt  13 . The second cam member  51  has a cylindrical shape, and is fixed to the cam shaft  50  with a positional relationship such that the cam shaft  50  passes through the second cam member  51  at a position offset from the center of the second cam member  51  by the distance d 1  (see  FIGS. 7(   a ) and ( b )). 
   As shown in  FIG. 3 , a pulley  55  is fixed to the cam shaft  50 . A gear  53  is provided that engages with the first cam member  43  of the driving side moving mechanism  41  (see  FIG. 5 ). The gear  53  has a pulley  53   a  that rotates integrally therewith A transmitting carrier belt  57  is wound across the pulley  53   a  and the pulley  55  that is fixed to the cam shaft  50 . Pulleys  54  and  56  exert tension on the transmitting carrier belt  57 . Due to the above, the second cam member  51  fixed to the cam shaft  50 , and the first cam member  43  of the driving side moving mechanism  41 , rotate with an identical rotation frequency. The pulleys  53   a ,  54 ,  55 , and  56  are capable of rotating with respect to the main chassis  30 . The gear  53  has a number of cogs such that, when the first cam member  43  has been rotated by means of the driving motor  24  when the gap is adjusted, the driving roller  11  and the driven roller  12  are raised or lowered by the same extent. As a result, a configuration is formed in which, when the gap is adjusted, the carrier belt  13  that is maintained by the belt chassis  10  is raised or lowered while always being supported in a parallel state with respect to the head faces  2   a.    
   As shown in  FIGS. 3 and 7 , both ends of the cam shaft  50  are supported by the main chassis  30 , via a shaft supporting member  52 , such that the cam shaft  50  can rotate. The second cam member  51  is fixed to the cam shaft  50  at both sides of the cam shaft  50 .  FIG. 3  shows only the second cam member  51  and the shaft supporting member  52  at a closer side relative to the plane of the page. In fact, a second cam member  51  and a shaft supporting member  52  are also present at a further side relative to the plane of the page. As described above, a center of the second cam member  51  is off-center by the distance d 1  from the central axis of the cam shaft  50 . This distance d 1  is identical with the distance d 1  between the rotational center of the cylindrical portion  43   c  of the first cam member  43  and the rotational center  11   a  of the driving roller  11 . 
   When the first cam member  43  is rotated by means of the driving motor  24 , the cam shaft  50  and the second cam member  51  fixed to the cam shaft  50  also rotate in synchrony with the rotation of the first cam member  43 . This alters the height of the lower edge of the second cam member  51 . As shown in  FIGS. 7(   a ) and ( b ), the height of the lower edge of the second cam member  51  can be raised or lowered between a position raised by the distance d 1  from a reference height shown in  FIG. 7(   a ), and a position lowered by the distance d 1  from the reference height shown in  FIG. 7(   b ). This is identical to the distance of upwards or downwards movement of the rotational center  11   a  of the driving roller  11 . The height of the lower edge of the second cam member  51  is raised or lowered following the height of the rotational center  11   a  of the driving roller  11 . 
   As shown in  FIGS. 1 and 2 , the belt chassis  10  is energized upwards, via the carrier belt receiving unit  14 , by a plurality of the compression springs  25 . As a result, a right end of the belt chassis  10  is pushed upwards so as to make contact with the lower edge of the second cam member  51 . When the height of the lower edge of the second cam member  51  changes, the right end of the belt chassis  10  follows it in moving upwards or downwards. 
   As shown in  FIGS. 1 and 4 , when the driving side moving mechanism  41  has raised the rotary shaft  11   a  of the driving roller  11  by the distance d 1  with respect to the main chassis  30 , the driven side moving mechanism  42  raises the right end of the belt chassis  10  by the distance d 1  with respect to the main chassis  30 , as shown in  FIG. 7(   a ). When the driving side moving mechanism  41  has lowered the rotary shaft  11   a  of the driving roller  11  by the distance d 1  with respect to the main chassis  30 , as shown in  FIG. 2 , the driven side moving mechanism  42  lowers the right end of the belt chassis  10  by the distance d 1  with respect to the main chassis  30 , as shown in  FIG. 7(   b ). 
   Since the driving side moving mechanism  41  and the driven side moving mechanism  42  operate in synchrony, the belt chassis  10  can move upwards or downwards while being maintained parallel to the main chassis  30 . 
   The driven side moving mechanism  42  has a parallel adjusting mechanism  60  for adjusting an upper face of the carrier belt  13  such that it becomes parallel to the ink discharging faces  2   a  of the eight ink jet heals  2 . 
   As shown in  FIGS. 7 and 8 , a cylindrical portion  52   a  is formed in the shaft supporting member  52  that supports the cam shaft  50 . The cylindrical portion  52   a  is supported in the main chassis  30  such that it can rotate. A shaft receiving hole  52   c  through which the cam shaft  50  passes is formed in the cylindrical portion  52   a . In the state shown in  FIG. 8 , a rotational center of the shaft receiving hole  52   c  is off-center, in a horizontal direction, by a determined quantity d 3  from a rotational center of the cylindrical portion  52   a.    
   As shown in  FIG. 8 , a circular arc-shaped groove  52   b  is formed in an upper edge portion of the shaft supporting member  52 . The circular arc-shaped groove  52   b  extends in the direction of rotation of the shaft supporting member  52 . The circular arc-shaped groove  52   b  has the same center as the cylindrical portion  52   a  As shown in  FIG. 3 , a screw  61  is passed through the groove  52   b , and the screw  61  is tightened to fix the shaft supporting member  52  to the main chassis  30 . When the screw  61  is loosened, the shaft supporting member  52  utilizes the cylindrical portion  52   a  to swing, within a vertical plane, with respect to the main chassis  30 . 
   As shown in  FIG. 8 , the rotational center of the cam shaft  50  is off-center, in a horizontal direction, by a determined quantity d 3  with respect to the center of the cylindrical portion  52   a  of the shaft supporting member  52 . Consequently, as shown in  FIG. 9(   a ), when the shaft supporting member  52  is rotated in an counterclockwise direction with the cylindrical portion  52   a  serving as the center, the cam shaft  50  rises by a determined quantity d 4 . Conversely, as shown in  FIG. 9  (b), when the shaft supporting member  52  is rotated in a clockwise direction, the cam shaft  50  is lowered by a determined quantity d 5 . In this manner, rotating the shaft supporting member  52  within a vertical plane enables the height (the position along a direction perpendicular to the head faces  2   a ) of the cam shaft  50  to be adjusted such that the height of the driving roller  11  and the height of the cam shaft  50  become identical. The carrier belt  13  can thus be adjusted so that it is parallel to the ink discharging faces  2   a.    
   Further, as shown in  FIGS. 1 and 2 , a guide member  62  and a pressing roller  63  are axially supported in the cam shaft  50 . The guide member  62  guides the paper to the ink jet heads  2 , and the pressing roller  63  presses, from above, the paper that is being carried to the ink jet heads  2 . The guide member  62  and the pressing roller  63  enable the paper to be carried smoothly to the ink jet heads  2 . Further, since the guide member  62  and the pressing roller  63  are disposed at the periphery of the cam shaft  50 , a more compact configuration of the ink jet printer  1  is possible. 
   The ink jet printer  1  is provided with a swinging mechanism  15  that swings the belt chassis  10  across a vertical plane with the rotary shaft  1   a  of the driving roller  11  as the center. When maintenance of the carrier unit  3  is required, or paper has jammed within the carrier unit  3 , the swinging mechanism  15  is activated to move the carrier unit  3  away from the ink discharging faces  2   a  of the ink jet heads  2 . 
   As shown in  FIG. 1 , the swinging mechanism  15  comprises a raising and lowering cam member  31 , a protrusion  31   a , a cam receiving member  32 , etc. The raising and lowering cam member  31  is supported in the main chassis  30  such that it can rotate. The protrusion  31   a  is formed integrally with the raising and lowering cam member  31 . The cam receiving member  32  is movable with respect to the belt chassis  10  in the vertical direction in  FIG. 1 . A stopper (not shown) is provided with the belt chassis  10 , and the stopper prevents from the cam receiving member  32  lowering further with respect to the belts chassis  10 . That is, when the cam receiving member  32  is lowered with respect to the main chassis  30 , the cam receiving member  32  abuts the stopper, and lowers the belts chassis  10  with respect to the main chassis  30 . The cam receiving member  32  has a cam groove  32   a  formed in its lower edge part. The protrusion  31   a  engages with the cam groove  32   a.    
   When the raising and lowering cam member  31  and the protrusion  31   a  rotate with respect to the main chassis  30 , the cam receiving member  32  is moved upward or downward with respect to the main chassis  30 . The belt chassis  10  may be movable vertically with respect to the cam receiving member  32 . The belt chassis  10  is pushed upward by the compression springs  25  with respect to the cam receiving member  32 . 
   A motor (not shown) is linked with the raising and lowering cam member  31 , and the motor rotates the raising and lowering cam member  31  with respect to the main chassis  30 . The protrusion  31   a , which protrudes in a cylindrical shape perpendicular to a face of the raising and lowering cam member  31  (a direction perpendicular to the face of the page of  FIG. 1 ), is formed at a location that is removed, in a radial direction, from a rotational center of the raising and lowering cam member  31 . When the raising and lowering cam member  31  rotates, the protrusion  31   a  moves along a concentric circle of the raising and lowering cam member  31 . The lower edge part of the cam receiving member  32  has the cam groove  32   a  formed therein, this extending in the longitudinal direction of the belt chassis  10  (the left-right direction of  FIG. 1 ). The protrusion  31   a  engages with the cam groove  32   a.    
   When the raising and lowering cam member  31  rotates, and the protrusion  31   a  moves along the concentric circle of the raising and lowering cam member  31 , the cam receiving member  32  changes its height with respect to the main chassis  10 . 
   During printing, the upper face of the carrier belt  13  is maintained such that it has been swung to an angle parallel to the ink discharging faces  2   a  of the ink jet heads  2 , as shown by the solid line in  FIG. 1 . In this position, the compression springs  25  push the belt chassis  10  upwards via the carrier belt receiving unit  14  with respect to the cam receiving member  32 . Lower ends of the compression springs  25  are supported by the main chassis  30  through the cam receiving member  32 , the protrusion  31   a  and the raising and lowering cam member  31 . Since the belt chassis  10  is pushed upward with respect to the main chassis  30 , the belt chassis  10  is lifted until the belt chassis  10  abuts the second cam member  51 . The upper face of the carrier belt  13  is maintained such that it has been swung to an angle parallel to the ink discharging faces  2   a  of the ink jet heads  2 . In the case where paper has jammed, or the like, the cam receiving member  32  is lowed by the rotation of the raising and lowering cam member  31 . When the cam receiving member  32  is lowered, it abuts the stopper of the belt chassis  10  and the belt chassis  10  is lowered As a result, the belt chassis  10  is swung downwards, as shown by the dashed line in  FIG. 1 , thereby removing the carrier unit  3  from the ink discharging faces  2   a  of the ink jet heads  2 . It is thus possible to remove the jammed paper. 
   A concave member  32   b  is formed in the cam groove  32   a . The concave member  32   b  has a circular arc shape and an upper end thereof is concave. When the belt chassis  10  is in a horizontal state, the cylindrical protrusion  31   a  engages with the concave member  32   b . The belt chassis  10  is supported by the raising and lowering cam member  31  via the protrusion  31   a , this preventing the belt chassis  10  from rattling while the paper is being delivered. Further, a notch  31   b  is formed in an outer peripheral portion of the raising and lowering cam member  31  at a determined location along the circumference thereof. A sensor (not shown) attached at the main chassis  30  side of the ink jet printer  1  detects the notch  31   b . This detection makes it possible to detect the angle of rotation of the raising and lowering cam member  31 , i.e., the degree of swinging of the carrier unit  3 . 
   Next, the operation of the ink jet printer  1  will be described. 
   First, in the case where the paper will be printed using the ink jet heads  2 , the output pulley  24   a  of the driving motor  24  is rotated in the counterclockwise direction, the driving force of the driving motor  24  is transmitted to the driving roller  11  via the carrier belt  22 , and the driving roller  11  is thus driven to rotate (see  FIGS. 1 ,  5 , and  6 ( a )). Thereupon, the carrier belt  13  wound across the driving roller  11  and the driven roller  12  moves, the carrier belt  13  delivers the paper to the ink jet heads  2  from the right side of  FIG. 1 , and ink is discharged to the paper from the ink jet heads  2 . At this juncture, as shown in  FIG. 4 , the protruding part  44   a  formed on the gear  44  that engages with the first cam member  43 , and the concave members  46   a  and  46   b  fixed to the main chassis  30 , prevent the rotation of the first cam member  43  that is engaging with the rotary shaft  11   a  of the driving roller  11 . Consequently, there is no change in the height of the driving roller  11  during its rotation (while delivering paper). 
   However, in the case where the type of paper being delivered makes it necessary to change the gap between the carrier belt  13  and the head faces  2   a  of the inkjet heads  2 , the driving motor  24  rotates in a clockwise direction (see  FIGS. 1 ,  5 , and  6 ( b )). Thereupon, the driving force of the driving motor  24  is transmitted to the first cam member  43 , and the first cam member  43  rotates. At this juncture, the rotary shaft  11   a  of the driving roller  11 , which is off-center with respect to the rotation of the first cam member  43 , moves upwards or downwards, thus allowing the gap at the driving roller  11  side to be adjusted. 
   Simultaneously, the driving force of the driving motor  24  is transmitted, via the gear  53 , the transmitting carrier belt  57 , etc., to the cam shaft  50  of the driven side moving mechanism  42 . Thereupon, in synchrony with the rotation of the first cam member  43 , the second cam member  51  fixed to the cam shaft  50  rotates, and the height of its lower edge changes. Since the belt chassis  10  is energized upwards by the plurality of compression springs  25 , the second cam member  51  and the belt chassis  10  are constantly maintained in a contacting state. When the height of the lower edge of the second cam member  51  changes, the portion of the belt chassis  10  at side of the driven roller  12  follows this height change and moves upwards or downwards. Consequently, the gap at the driven roller  12  side is adjusted. At this juncture, the belt chassis  10  is raised or lowered while being maintained parallel to the ink discharging faces  2   a , and the driving roller  11  and the driven roller  12  are maintained at the same height. 
   In the case where thin paper, photographic paper, etc. is to be printed, the state is switched to that shown in  FIG. 1 , in which the gap is narrow. Conversely, in the case where thick paper such as envelopes, etc. is to be printed, the state is switched to that shown in  FIG. 2 , in which the gap is wide. 
   The adjustment of the gap, using the moving mechanism  40  described above, can be performed on the basis of information input by an operator concerning paper type, by using a controlling device (not shown) of the ink jet printer  1  to drive the driving motor  24 . Alternatively, a sensor can be provided to detect the type of paper delivered to the inkjet heads  2  from a paper supply tray, and the controlling device can drive the motor  24  to adjust the gap on the basis of a signal from the sensor. 
   In the moving mechanism  40  described above, the driving side moving mechanism  41  raises or lowers a portion of the belt chassis  10  at the side of the driving roller  11 , and in synchrony with the driving side moving mechanism  41 , the driven side moving mechanism  42  raises or lowers a portion of the belt chassis  10  at the side of the driven roller. Consequently, the gap between the head faces  2   a  and the carrier belt  13  can be adjusted while the carrier belt  13  is being maintained in a parallel state with respect to the head  2   a . As a result, printing quality can be improved, and paper can be delivered smoothly to the ink jet heads  2 . 
   Next, variants of the above embodiment will be described. Components configured identically to those of the above embodiment have the same reference numbers assigned thereto and a description thereof is omitted. 
   The motor for rotating the first cam member  43  can be different from the driving motor  24  that rotates the driving roller  11 . In this case, a configuration is not required in which the motor for rotating the driving roller  11  and the motor for rotating the first cam member  43  are common, and consequently the configuration of the driving side moving mechanism can be simplified. 
   The motor for rotating the cam shaft  50  of the driven side moving mechanism  42  may equally well be different from the motor for rotating the first cam member  43  of the driving side moving mechanism  41  (the driving motor  24  in the embodiment described above), and the driving side moving mechanism  41  and the driven side moving mechanism  42  may be synchronized by means for electrically causing the synchronization of these two motors. Furthermore, the driving side moving mechanism  41  and the driven side moving mechanism  42  need not necessarily be made to operate in synchrony. For example, the driven side moving mechanism  42  can raise or lower the belt chassis  10  at the side of the driven roller  12  after the driving side moving mechanism  41  has raised or lowered the belt chassis  10  at the side of the driving roller. That is, it is equally possible for the carrier belt  13  to be made parallel to the head faces  2   a  at a final stage in adjusting the gap. 
   In the above embodiment, the moving mechanism  40  is a configuration in which the location of the carrier belt  13  can be switched between either a location in which the gap is narrow (see  FIG. 1 ), or a location in which the gap is wide (see  FIG. 2 ). However, a configuration is equally possible in which the location of the carrier belt  13  can be selected from between three or more locations (that is, there are three or more types of gap). Furthermore, in the case where the driving motor is a stepping motor, a configuration is possible in which the gap can be finely adjusted for each of the driving steps of the stepping motor when the gap is being adjusted. 
   The present invention can be applied to printing heads other than ink jet heads, such as those of a thermal printer, a dot printer, etc. 
   If the carrier belt  13  is shifted into a parallel position from a starting position, the gap between the carrier belt  13  and the ink jet head  2  is maintained uniform along the delivery direction. The carrier belt  13  needs not move in a parallel manner while the moving mechanism  40  is operating. However, if the carrier belt  13  is maintained in a parallel manner while the moving mechanism  40  is operating, the gap can easily be adjusted as desired. Furthermore, the moving mechanism can easily be simplified. The embodiment of the moving mechanism  40  causes the carrier belt  13  to constantly move in a parallel manner. 
   It is preferred that the carrier unit  3  has the belt chassis  10  that is separate from the main chassis  30  of the main body of the printer  1 . 
   The use of two chassis  10 ,  30  simplifies the moving mechanism  40 . 
   A pair of rollers  11 ,  12  is supported, such that they can rotate, in the belt chassis  10 . It is preferred that the moving mechanism  40  is provided with two adjusting mechanisms  41  and  42 . One of the adjusting mechanisms  41  changes the height of the rotary shaft  11   a  of one of the rollers. The other adjusting mechanism  42  changes the height, by the same distance, of an end of a belt chassis  10  at the side supporting the other roller  12 . 
   In the case where one of the adjusting mechanisms  41  moves the rotary shaft  11   a , and the other adjusting mechanism  42  moves the belt chassis  10 , the movement of the two mechanism  41 ,  42  may be independent in the delivery direction, and the configuration of the moving mechanism  40  is thus simplified. 
   It is preferred that the moving mechanism  41  for shifting the rotary shaft  11   a  shifts the rotary shaft  1   a  of the driving roller  11  of the carrier belt  13 . This makes it easier for the driving source for changing the height of the rotary shaft  11   a  of the driving roller  11  to also function as the driving source for driving the carrier belt  13 . 
   It is preferred that a cylindrical portion  43   c  capable of being rotated with respect to the main chassis  30  supports the rotary shaft  11   a  of the driving roller  11 , in a manner allowing rotation of the driving roller  11 , at a location offset from a rotational center of the cylindrical portion  43   c . In the present specification, the cylindrical portion  43   c  supporting the rotary shaft  11   a  of the driving roller  11  in this manner is turned the first cam member  43 . 
   In this case, the height of the rotary shaft  11   a  of the driving roller  11  is changed when the first cam member  43  is rotated with respect to the main chassis  30 . 
   It is preferred that the moving mechanism  42  that changes the height of the end of the belt chassis  10  at the side of the driven roller  12  does not restrict the movement of the belt chassis  10  in the delivery direction. 
   The rotary shaft  11   a  of the driving roller  11  also moves in the delivery direction when the first cam member  43  is rotated with respect to the main chassis  30 . If the mechanism for changing the height of the end of the belt chassis  10  at the side of the driven roller  12  does not restrict the movement of the belt chassis  10  in the delivery direction, there will be no inconsistent movement between the two sides. 
   It is preferred that a motor for rotating the first cam member  43  with respect to the main chassis  30  also functions as a motor causing the rotation of the rotary shaft  11   a  of the driving roller  11 . The number of motors required can thus be reduced, and consequently the cost of manufacturing the printer  1  can be reduced. 
   It is preferred that a restraining mechanism  44   a ,  46   a  and  46   b  is provided that prohibits rotation of the first cam member  43  while the rotary shaft  11   a  of the driving roller  11  is rotating. This prevents a change of position of the driving roller  11  while the driving roller  11  is rotating so as to deliver the sheet. 
   It is preferred that the moving mechanism  42  that changes the height of the end of the belt chassis  10  at the side supporting the driven roller  12  is provided with the cam shaft  50  and the second cam member  51  in which the distance from the rotating center of the cam shaft  50  to the tip of the second cam member  51  changes in a circumference direction. The moving mechanism  42  directly changes the height of the belt chassis  10  at the side of the driven roller  12 , and indirectly changes the height of the driven roller  12 . In this case, the degree of change in height of the belt chassis  10  at the side of the driven roller  12  caused by the second cam member  51 , the degree of change in height of the driven roller  12  caused by the second cam member  51  and the degree of change in height of the driving roller  11  caused by the first cam member  43  can be made identical, and consequently the belt chassis  10  can be moved in a parallel manner and the driving roller  11  and driven roller  12  changes in height by the same amount. 
   It is preferred that a motor for causing the rotation of the first cam member  43  also serves as a motor for causing the cam shaft  50  to rotate. 
   Not only does this reduce the number of motors required and thus reduce the cost of manufacturing the printer, but it also enables the degree of change in height caused by the first cam member  43 , and the degree of change in height caused by the second cam member  51  to usually be maintained so as to be identical. 
   It is preferred that the guiding member  62  for guiding the sheet towards the printing head  2 , and the pressing roller  63  for pressing the sheet towards the carrier belt  13 , are supported, in a manner allowing rotation, in the cam shaft  50 . The printer  1  can have a compact configuration if the guiding member  62  and the pressing roller  63  are disposed at a periphery of the cam shaft  50 . 
   It is preferred that the parallel adjusting mechanism  60  is provided between the main chassis  30  and the cam shaft  50 . This parallel adjusting mechanism  60  is capable of changing the height of the cam shaft  50  with respect to the main chassis  30 . It is thus easy to adjust the degree of parallelization of the carrier belt  13  with respect to a head face  2   a.