Patent Publication Number: US-11654704-B2

Title: Recording apparatus

Description:
The present application is a Continuation of U.S. patent application Ser. No. 16/799,397, filed Feb. 24, 2020, which claims priority from JP Application Serial Number 2019-033848, filed Feb. 27, 2019, and JP Application Serial Number 2019-183590, filed Oct. 4, 2019, the disclosures of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a recording apparatus that performs recording on a medium. 
     2. Related Art 
     A recording apparatus represented by a printer is provided with a recording head that is mounted on a carriage reciprocating in a width direction of a medium and ejects an ink, which is a liquid, toward the medium, and is configured to perform recording on the medium by ejecting the ink while moving the recording head in the width direction. The medium is sent toward the recording head by a transport unit such as a transport roller. 
     The medium transported by the transport unit is supported from the lower side by a medium supporting member provided at a position facing the recording head. Accordingly, a paper gap, which is a distance between a recording surface of the medium and the recording head, is defined. In the following, the paper gap may be abbreviated as PG. 
     When a distance between the recording head and the medium supporting member is fixed, the PG is changed according to the thickness of the medium. Since the change in the PG affects image quality, there is a possibility that the image quality may deteriorate due to a difference in the thickness of the medium. In order to suppress influence on the image quality due to the difference in the thickness of the medium, for example, JP-A-2007-144766 discloses a recording apparatus including a gap adjustment member that adjusts the PG by changing the height of the recording head according to the thickness of the medium. 
     The gap adjustment member disclosed in JP-A-2007-144766 includes a stepped portion which is slidable in a width direction and of which the height is changed in a stepwise manner in a slide direction. A support member that can be displaced in a height direction is disposed to come into contact with the stepped portion. The support member is provided on the carriage. When the support member is displaced in the height direction, the heights of the carriage and the recording head mounted on the carriage are also changed. When the gap adjustment member is slid, the support member is displaced in the height direction along the stepped portion, and the height of the recording head is also changed. 
     As in JP-A-2007-144766, when a height of a recording head is changed by displacing a support member along a stepped portion of a gap adjustment member, in a case in which the support member moves from a high step to a low step of the stepped portion, the carriage may fall by a height corresponding to a step difference due to a self-weight thereof, and thus a loud sound may be generated. 
     SUMMARY 
     According to an aspect of the present disclosure, there is provided a recording apparatus including a recording head that performs recording on a medium that is transported, a carriage that has the recording head mounted thereon and is movable in a width direction intersecting a transport direction of the medium, a guide member that extends in the width direction and guides the carriage, and a gap adjustment unit that displaces the carriage in a first axis direction to change a gap between the recording head and a support surface. The gap adjustment unit has a sliding member that moves in the width direction integrally with the carriage while the sliding member slides with respect to the guide member, and a cam member that is interposed between the carriage and the sliding member and has a stepped portion in which a maintenance surface that maintains a position of the carriage in the first axis direction and an adjustment surface that changes the position of the carriage in the first axis direction are alternately arranged in the width direction. The gap adjustment unit is configured such that the cam member slides in the width direction with respect to the carriage and the sliding member to change the gap. The gap adjustment unit includes a buffer unit that decreases a displacement speed of the carriage in the first axis direction when the gap is reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an external perspective view of a printer according to Embodiment 1. 
         FIG.  2    is a perspective view illustrating a state in which a scanner unit is completely opened in the printer according to Embodiment 1. 
         FIG.  3    is a side sectional view of the printer according to Embodiment 1. 
         FIG.  4    is a perspective view illustrating a state in which a document table cover of the scanner unit is opened in the printer according to Embodiment 1. 
         FIG.  5    is a perspective view illustrating a state in which a carriage is moved to a position when the ink is replenished in a liquid accommodating unit, in the printer according to Embodiment 1. 
         FIG.  6    is a cross-sectional view taken along line VI-VI in  FIG.  3    of the carriage, and is a view illustrating a state in which a contact portion of a sliding member is in contact with a fourth maintenance surface of a stepped portion of a cam member. 
         FIG.  7    is a cross-sectional view taken along line VII-VII in  FIG.  3    of the carriage, and is a view illustrating a state in which the contact portion of the sliding member is in contact with a first maintenance surface of the stepped portion of the cam member. 
         FIG.  8    is a schematic view illustrating a main portion of  FIG.  6   . 
         FIG.  9    is a diagram for illustrating a gap adjustment unit according to Embodiment 2. 
         FIG.  10    is a diagram for illustrating the gap adjustment unit according to Embodiment 2. 
         FIG.  11    is a diagram for illustrating a gap adjustment unit according to Embodiment 3. 
         FIG.  12    is a diagram for illustrating a gap adjustment unit according to Embodiment 4. 
         FIG.  13    is a diagram for illustrating a gap adjustment unit according to Embodiment 5. 
         FIG.  14    is a perspective view illustrating a carriage including the gap adjustment unit having an auxiliary adjustment unit. 
         FIG.  15    is a side view of the carriage illustrated in  FIG.  14   . 
         FIG.  16    is a cross-sectional view taken along line XVI-XVI in  FIG.  15   , and is a view illustrating a state in which the carriage is located in a fourth position in a Z-axis direction. 
         FIG.  17    is a cross-sectional view taken along line XVII-XVII in  FIG.  15   , and is a view illustrating a state in which the carriage is located in a first position in a Z-axis direction. 
         FIG.  18    is a perspective view for illustrating another gap adjustment unit. 
         FIG.  19    is a sectional view taken along line XIX-XIX in  FIG.  18   . 
         FIG.  20    is a diagram for illustrating a gap adjustment unit according to Embodiment 6. 
         FIG.  21    is a diagram for illustrating the gap adjustment unit according to Embodiment 6. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, the present disclosure will be schematically described. 
     According to an aspect of the present disclosure, there is provided a recording apparatus including a recording head that performs recording on a medium that is transported, a carriage that has the recording head mounted thereon and is movable in a width direction intersecting a transport direction of the medium, a guide member that extends in the width direction and guides the carriage, and a gap adjustment unit that displaces the carriage in a first axis direction to change a gap between the recording head and a support surface. The gap adjustment unit has a sliding member that moves in the width direction integrally with the carriage while the sliding member slides with respect to the guide member, and a cam member that is interposed between the carriage and the sliding member and has a stepped portion in which a maintenance surface that maintains a position of the carriage in the first axis direction and an adjustment surface that changes the position of the carriage in the first axis direction are alternately arranged in the width direction. The gap adjustment unit is configured such that the cam member slides in the width direction with respect to the carriage and the sliding member to change the gap. The gap adjustment unit includes a buffer unit that decreases a displacement speed of the carriage in the first axis direction when the gap is reduced. 
     According to this aspect, the gap adjustment unit includes a sliding member that moves in the width direction integrally with the carriage while the sliding member slides with respect to the guide member, a cam member that is interposed between the carriage and the sliding member, includes the stepped portion, and slides in the width direction to displace the carriage in the first axis direction with respect to the sliding member, and a buffer unit that decreases a displacement speed of the carriage in the first axis direction. Thus, the carriage can be displaced slowly, and sound generated when the carriage is displaced can be suppressed. 
     A second aspect of the present disclosure provides the recording apparatus according to the first aspect, in which the buffer unit acts on the carriage that displaces in a direction including a vertical downward component in the first axis direction, and does not act on the carriage that displaces in a direction including a vertical upward component in the first axis direction. 
     According to this aspect, the buffer unit acts on the carriage displaced in a direction including a vertical downward component in the first axis direction and does not act on the carriage displaced in a direction including a vertical upward component. Therefore, when the carriage is displaced in the direction including the vertical downward component, the carriage is decelerated by the buffer unit, the carriage is vigorously displaced due to a self-weight thereof, and thus, a possibility that a loud sound occurs can be reduced. On the other hand, since the buffer unit does not act when the carriage is displaced upward, an increase in a load when the carriage is displaced upward can be suppressed. 
     A third aspect of the present disclosure provides the recording apparatus according to the second aspect, in which the stepped portion includes, as the maintenance surface, a first maintenance surface that maintains the position of the carriage with respect to the sliding member at a first position, a second maintenance surface that maintains the position of the carriage with respect to the sliding member at a second position at which the gap is smaller than the gap at the first position, and a third maintenance surface that maintains the position of the carriage with respect to the sliding member at a third position at which the gap is smaller than the gap at the second position, a height difference between the first position and the second position in the first axis direction is larger than a height difference between the second position and the third position in the first axis direction, and the buffer unit acts when the gap is changed from a size defined at the first position to a size defined at the second position, and does not act when the gap is changed from the size defined at the second position to a size defined at the third position. 
     According to this aspect, only when a loud sound is likely to be generated since the carriage is greatly displaced downward, the buffer unit acts on the carriage, so that generation of the sound due to the displacement of the carriage can be effectively suppressed. 
     A fourth aspect of the present disclosure provides the recording apparatus according to any of the first aspect to the third aspect, in which the buffer unit includes a rack and pinion mechanism, a rack constituting the rack and pinion mechanism is provided on the sliding member along the first axis direction, a pinion gear constituting the rack and pinion mechanism is provided on the carriage, and resistance is applied to the pinion gear upon rotation, and the displacement speed of the carriage is reduced. 
     According to this aspect, since the buffer unit includes the rack and pinion mechanism, and rotational resistance is applied to the pinion gear constituting the rack and pinion mechanism, the buffer unit can be configured with a simple structure at low costs. 
     A fifth aspect of the present disclosure provides the recording apparatus according to the fourth aspect, in which the buffer unit is configured to apply the resistance to the pinion gear by a damper. 
     According to this aspect, a simple configuration can be achieved in which the rotational resistance is applied to the pinion gear. 
     A sixth aspect of the present disclosure provides the recording apparatus according to the fourth aspect, in which the buffer unit includes a driven gear that engages with the pinion gear and is driven to rotate, and a reduction gear ratio when power is transmitted from the pinion gear to the driven gear is larger than 1, and the driven gear applies the resistance to the pinion gear. 
     According to this aspect, a simple configuration can be achieved in which the rotational resistance is applied to the pinion gear. 
     A seventh aspect of the present disclosure provides the recording apparatus according to any of the first aspect to the third aspect, in which the buffer unit includes an elastic member provided between the sliding member and the carriage, and the displacement speed of the carriage is reduced by elasticity of the elastic member. 
     According to this aspect, an elastic member provided between the sliding member and the carriage is used as the buffer unit, so that the same effect as any of the first to third aspects can be achieved with a simple configuration. 
     An eighth aspect of the present disclosure provides the recording apparatus according to any of the first aspect to the third aspect, in which the buffer unit includes a rack and pinion mechanism, a rack constituting the rack and pinion mechanism is provided on the cam member along the width direction, a pinion gear constituting the rack and pinion mechanism is provided on the carriage, and resistance is applied to the pinion gear upon rotation, and the displacement speed of the carriage is reduced. 
     According to this aspect, since the rack constituting the rack and pinion mechanism is provided on the cam member along the width direction, the length of the rack can be increased, and the rotation amount of the pinion gear can be further secured. Therefore, influence of a backlash in meshing of gears can be reduced, and the sound generated when the carriage is displaced can be suppressed more reliably. 
     A ninth aspect of the present disclosure provides the recording apparatus according to the eighth aspect, in which the cam member displaces in an area in a direction opposite to a direction of a home position of the carriage with respect to a central position of the carriage in the width direction, and the buffer unit is provided in the direction opposite to the direction of the home position of the carriage with respect to the central position of the carriage in the width direction. Accordingly, an increase in the size of the apparatus can be suppressed. Details thereof will be described later. 
     A tenth aspect of the present disclosure provides a recording apparatus including a recording head that performs recording on a medium that is transported, a carriage that has the recording head mounted thereon and is movable in a width direction intersecting a transport direction of the medium, a guide member that extends in the width direction and guides the carriage, and a gap adjustment unit that displaces the carriage in a first axis direction to change a gap between the recording head and a support surface. The gap adjustment unit has a sliding member that moves in the width direction integrally with the carriage while the sliding member slides with respect to the guide member, and a cam member that is interposed between the carriage and the sliding member and has a stepped portion in which a maintenance surface that maintains a position of the carriage in the first axis direction and an adjustment surface that changes the position of the carriage in the first axis direction are alternately arranged in the width direction. The gap adjustment unit is configured such that the cam member slides in the width direction with respect to the carriage and the sliding member to change the gap. The stepped portion includes, as the maintenance surface, a first maintenance surface that maintains a position of the carriage with respect to the sliding member at a first position, a second maintenance surface that maintains the position of the carriage with respect to the sliding member at a second position at which the gap is smaller than the gap at the first position, and a third maintenance surface that maintains the position of the carriage with respect to the sliding member at a third position at which the gap is smaller than the gap at the second position. A height difference between the first position and the second position in the first axis direction is larger than a height difference between the second position and the third position in the first axis direction. The stepped portion includes, as the adjustment surface, a first adjustment surface that couples the first maintenance surface and the second maintenance surface and a second adjustment surface that couples the second maintenance surface and the third maintenance surface. An inclination angle of the first adjustment surface with respect to a horizontal plane is smaller than an inclination angle of the second adjustment surface with respect to the horizontal plane. 
     According to this aspect, in the stepped portion, an inclination angle of the first adjustment surface that is an adjustment surface for changing the position of the carriage from the first position to the second position is smaller than an inclination angle of the second adjustment surface that is an adjustment surface for changing the position of the carriage from the second position to the third position. Thus, when the carriage is displaced more greatly, the first adjustment surface is used, and a sound generated with the displacement of the carriage can be reduced. 
     Embodiment 1 
     Hereinafter, an outline of a recording apparatus according to an embodiment of the present disclosure will be described. In the present embodiment, an ink jet printer  1  is described as an example of the recording apparatus. Hereinafter, the ink jet printer  1  is simply referred to as a printer  1 . 
     In an XYZ coordinate system illustrated in each drawing, an X-axis direction indicates an apparatus width direction, a Y-axis direction indicates an apparatus depth direction, and a Z-axis direction indicates an apparatus height direction. Further, the +Y direction indicates a forward direction of the apparatus, and the −Y direction indicates a rearward direction of the apparatus. Further, when viewed from the forward direction of the apparatus, a leftward direction indicates the +X direction, and a rightward direction indicates the −X direction. Further, the +Z direction indicates an upward direction, and the −Z direction indicates a downward direction. 
     Further, in the printer  1 , a transport direction in which a medium is transported is referred to as a “downstream direction”, and a direction that is opposite thereto is referred to as an “upstream direction”. 
     Outline of Printer 
     The printer  1  illustrated in  FIG.  1    includes a housing  2  that includes a recording unit  8  that performs recording on a medium, and a scanner unit  4  that is provided on the housing  2  and reads an image of a document. That is, the printer  1  is configured as a multi-function machine having an image reading function in addition to a recording function. 
     In the printer  1 , examples of the medium on which the recording is performed include, in addition to plain paper, thick paper that is thicker than the plain paper, such as a postcard and a business card, thin paper that is thinner than the plain paper, glossy paper for photography, and the like. Further, the printer  1  is configured to also perform recording on a label surface of a disc-type memory such as a CD and a DVD. 
     In the printer  1 , the recording unit  8  includes a recording head  10  that performs recording on the medium by ejecting an ink as a liquid, and a carriage  20  that supports the recording head  10 , and is configured to perform the recording by ejecting the ink from the recording head  10  toward the medium P. 
     The carriage  20  is configured to reciprocate in the X-axis direction that is a width direction intersecting the transport direction of the medium P. 
     The scanner unit  4  is provided to be pivotable with respect to the housing  2  and is configured to be able to open and close an upper portion of the housing  2  through pivot.  FIG.  1    illustrates a closed state in which the scanner unit  4  is closed with respect to the housing  2 , and  FIG.  2    illustrates an opened state in which the scanner unit  4  is completely opened with respect to the housing  2 . 
     A panel unit  13  including an operation unit  6  is provided in the +Y direction that is the forward direction of the printer  1 . The operation unit  6  can perform preview display of setting contents or an image in addition to various setting operations and execution operations for recording and image reading. 
     The panel unit  13  is provided in the scanner unit  4 , and is configured to be pivotable from a state in which an operation surface  6   a  illustrated in  FIG.  1    faces the front side in a direction in which the operation surface  6   a  faces the upper side. 
     A lower cover  7  is provided at a lower portion of a front surface  2   a  of the housing  2 . The front surface  2   a  of the housing  2  is not visible in  FIG.  1    but is illustrated in  FIG.  2   . 
     By opening the lower cover  7  as indicated by a dotted line in  FIG.  3   , a medium tray  11  for accommodating the medium P before recording and a discharge tray  12  for receiving the medium P discharged after the recording are exposed. 
     The discharge tray  12  can be switched between a storage state in which the discharge tray  12  is stored in the housing  2  as indicated by a solid line in  FIG.  3    and a protrusion state in which the discharge tray  12  protrudes toward the front side of the housing  2  as indicated by a dotted line in  FIG.  3   , and can receive the medium P after recording in the protrusion state. The discharge tray  12  is configured to be switchable between the storage state and the protrusion state by a drive source that is not illustrated. 
     The medium tray  11  can accommodate a plurality of media P, and is detachable from the housing  2 . As illustrated in  FIG.  3   , the medium tray  11  can send the medium P to a medium transport path T, which will be described below, while being mounted on the housing  2 . Further, the medium tray  11  can be replenished with the medium P while being pulled out forward (in the +Y direction). 
     In Medium Transport Path in Printer 
     Next, the medium transport path T of the printer  1  will be described with reference to  FIG.  3   . The medium transport path T is a transport path for the medium P transported from the medium tray  11  provided at a lower portion of the printer  1  toward an area in which recording is performed by the recording unit  8 . 
     The medium P set on the medium tray  11  is picked up by the feeding roller  16  and is sent out to the medium transport path T. In more detail, the feeding roller  16  that is rotationally driven by the drive source that is not illustrated is provided in a roller support member  19  that swings about a swing shaft  19   a , rotates while being in contact with the uppermost medium P of the plurality of media P accommodated in the medium tray  11 , and sends out the uppermost medium P from the medium tray  11  in the rearward direction of the apparatus (in the −Y direction). 
     An intermediate roller  17  that is rotationally driven by the drive source that is not illustrated is provided downstream of the feeding roller  16 , and the medium P is curved and reversed by the intermediate roller  17 , and is sent in the forward direction of the apparatus (in the +Y direction). Reference numerals  18   a ,  18   b ,  18   c , and  18   d  are driven rollers that can be driven and rotated by the intermediate roller  17 , and the medium P is nipped by the driven roller  18   a  and the intermediate roller  17 , is nipped by the driven roller  18   b  and the intermediate roller  17 , is then nipped by the driven roller  18   c  and the intermediate roller  17 , and is sent downstream. The driven roller  18   d  will be described later. 
     A transport roller pair  21  is provided downstream of the intermediate roller  17 , and the medium P is sent to a lower side of the recording head  10  by the transport roller pair  21 . In  FIG.  3   , the transport roller pair  21  has a lower roller rotationally driven by the drive source that is not illustrated, and an upper roller driven and rotated by the lower roller. 
     The recording unit  8  including the recording head  10  and the carriage  20  is provided downstream of the transport roller pair  21 . The recording head  10  that ejects the ink is provided at the bottom of the carriage  20 . A liquid accommodation portion  24  for accommodating the ink supplied to the recording head  10  is mounted on the carriage  20 . In other words, the housing  2  includes the liquid accommodation portion  24  therein. 
     The liquid accommodation portion  24  can be replenished with the ink, the amount of which is reduced by recording. As in  FIG.  3   , in a state in which the scanner unit  4  is opened, the liquid accommodation portion  24  is replenished with the ink. A plurality of the liquid accommodation portions  24  corresponding to a plurality of colors are mounted on the carriage  20 . A cap  26  for closing an ink supply port  25  illustrated in  FIG.  5    is provided on each liquid accommodation portion  24 .  FIG.  5    illustrates a state in which the cap  26  of the leftmost liquid accommodation portion  24  is opened when the drawing is viewed from the front side. The cap  26  opens and closes the ink supply port  25  by pivoting about the rearward direction of the apparatus (the −Y direction). The ink can be poured into the liquid accommodation portion  24  from the ink supply port  25 . 
     Further, the liquid accommodation portion  24  can be disposed inside or outside the housing  2  without being mounted on the carriage  20  and can be configured to supply the ink to the recording head  10  via a tube. 
     In  FIG.  2   , the carriage  20  is located at a home position. The home position is provided at one end of a moving area of the carriage  20 , and is set at an end in the −X direction in the present embodiment. An eaves member  14  is provided in front of the housing  2  in the −X direction, and when the carriage  20  is located at the home position, the liquid accommodation portion  24  with the cap  26  closed is located below the eaves member  14 . The carriage  20  can be located at the home position by the eaves member  14  with the cap  26  securely closed. 
     Since the eaves member  14  exists, the cap  26  of the liquid accommodation portion  24  cannot be opened when the carriage  20  is located at the hoe position. When the liquid accommodation portion  24  is replenished with the ink, for example, an ink replenishment mode is selected in the operation unit  6 , so that the carriage  20  can be moved to a position where the cap  26  is not covered by the eaves member  14 , as illustrated in  FIG.  5   . 
     As illustrated in  FIG.  2   , a notch  15  is provided in the front surface  2   a  of the housing  2 . A window portion  27  that allows the user to visually recognize the amount of the ink therein is provided on a side surface of the liquid accommodation portion  24  in the +Y direction. In the ink replenishment mode, the carriage  20  is moved to a position where the carriage  20  overlaps the notch  15  in the X-axis direction as illustrated in  FIG.  5   . Accordingly, the ink can be replenished while the user checks the amount of the ink in the liquid accommodation portion  24 . 
     When the replenishment of the ink is completed, for example, the ink replenishment mode is terminated in the operation unit  6 , so that the carriage  20  can return to the home position. Further, it is detected that the scanner unit  4  is closed with respect to the housing  2 , and the carriage  20  returns to the home position using the detection result as a trigger. 
     The carriage  20  reciprocates in the width direction (the X-axis direction) by the drive source that is not illustrated. The printer  1  includes a guide member  28  extending in the width direction as illustrated in  FIG.  2   , and the carriage  20  moves in the width direction along the guide member  28 . The guide member  28  guides the carriage  20  in the width direction. 
     In  FIG.  3   , a medium support member  23  that forms a support surface that supports the medium P transported through the medium transport path T is provided in a position facing the recording head  10 . The upper surface of the medium support member  23  serves as the support surface of the medium P. The medium P is supported on the medium support member  23 , and an interval between the medium P and the recording head  10  is defined. 
     The interval between the medium P and the recording head  10 , which is suitable for the recording, varies depending on the type of the medium P. Therefore, the printer  1  includes a gap adjustment unit  40  that displaces the carriage  20  in a first axis direction in which a gap between the recording head  10  and the medium support member  23  (the support surface) that supports the medium P at a position where the medium support member  23  faces the recording head  10  changes. In the present embodiment, the first axis direction is the Z-axis direction. The gap adjustment unit  40  will be described below. 
     A discharge roller pair  22  is provided downstream of the medium support member  23 . Similar to the transport roller pair  21 , the discharge roller pair  22  is also configured such that a lower roller is rotationally driven by a drive source that is not illustrated, and an upper roller is driven and rotated by the lower roller. The medium P after recording by the recording unit  8  is discharged by the discharge roller pair  22  toward the discharge tray  12  in the protrusion state as indicated by a dotted line in  FIG.  3   . 
     The printer  1  is configured to be able to perform double-sided recording in which recording is performed on a first surface of the medium P and a second surface opposite to the first surface. When performing the double-sided recording, after the recording on the first surface, the medium P is switched back and is sent in the −Y direction. The switched-back medium P can be nipped by the driven roller  18   d  and the intermediate roller  17  and can be joined to the medium transport path T. The medium P is reversed by the intermediate roller  17  and is transported to the lower side of the recording head  10  in a state in which the second surface faces the recording head  10 , and the recording is performed on the second surface. 
     Further, the printer  1  is configured to be able to supply the medium P, on which the recording is performed, also from an upper supply port  9  provided at an upper portion in the rearward direction of the apparatus. The upper supply port  9  is opened by opening a feeding port cover  3 . The medium P supplied from the upper supply port  9  enters the medium transport path T from upstream of the transport roller pair  21 , and the recording on the medium P is performed by the recording head  10 . 
     In Scanner Unit 
     In the printer  1 , as illustrated in  FIG.  2   , the scanner unit  4  is provided to be pivotable with respect to the upper portion of the housing  2 . The scanner unit  4  has a pivot shaft in the rearward direction of the apparatus, that is, the −Y direction, and pivots with an end in the forward direction of the apparatus, that is, the +Y direction, as a free end  4   a . The scanner unit  4  is configured to be able to open and close the upper portion of the housing  2  through pivot. 
     As illustrated in  FIG.  3   , the scanner unit  4  includes a scanner body  30  that includes a reading unit  31  therein, and a document table cover  5  that can open and close a document table  32  provided at an upper portion of the scanner body  30 . When the document table cover  5  is opened as illustrated in  FIG.  4   , the document table  32  is exposed. The reading unit  31  illustrated in  FIG.  3    reads a document placed on the document table  32 . The document is placed on the document table  32  in a state in which a reading surface faces the document table  32 . 
     When the document table cover  5  is closed, as illustrated in  FIG.  4   , a presser plate  33  that presses the document is provided on a surface facing the document table  32 . 
     The panel unit  13  is provided in the scanner body  30 , and the document table cover  5  can be opened and closed alone. 
     In Gap Adjustment Unit 
     Hereinafter, the gap adjustment unit  40  will be described in detail. 
     The gap adjustment unit  40  includes a sliding member  50  and a cam member  60 , illustrated in  FIG.  6   . Then, the gap adjustment unit  40  is configured to change a gap when the cam member  60  slides in the width direction with respect to the carriage  20  and the sliding member  50 . 
     Hereinafter, a configuration in which the gap adjustment unit  40  changes the gap will be described in detail. 
     The sliding member  50  can move in the width direction (the X-axis direction) integrally with the carriage  20  while sliding with respect to the guide member  28  illustrated in  FIGS.  2  and  3   . 
     In more detail, in  FIG.  6   , sliding portions  51  that are in contact with the guide member  28  are provided at both ends of a lower surface  50   a  of the sliding member  50  in the width direction. Further, regulation portions  52  that abut on the carriage  20  and regulate movement of the sliding member  50  in the width direction with respect to the carriage  20  are provided at both ends of the sliding member  50  in the width direction. The carriage  20  is provided to be displaceable in the Z-axis direction, which is the first axis direction, without changing the position thereof in the width direction with respect to the sliding member  50 . 
     Further, a contact portion  53  that is in contact with a stepped portion  63  of the cam member  60 , which will be described below, is provided at an upper portion of the sliding member  50 . 
     As illustrated in  FIG.  6   , the cam member  60  is interposed between the carriage  20  and the sliding member  50  and has the stepped portion  63  in which a maintenance surface  61  that maintains the position of the carriage  20  in the first axis direction (the Z-axis direction), and an adjustment surface  62  that changes the position of the carriage  20  in the first axis direction are alternately arranged in the width direction. The maintenance surface  61  is formed on a horizontal plane that intersects the Z-axis direction that is the first axis direction, and the adjustment surface  62  is formed on an inclined surface that couples the two maintenance surfaces  61  having different heights. 
     In the present embodiment, the stepped portion  63  includes, as the maintenance surface  61 , a first maintenance surface  61   a  which maintains the position of the carriage  20  with respect to the sliding member  50  at a first position Z 1  illustrated in  FIGS.  7  and  8   , a second maintenance surface  61   b  which maintains the position at a second position Z 2  having a gap G (see  FIG.  8   ) that is smaller than that of the first position Z 1 , a third maintenance surface  61   c  which maintains the position at a third position Z 3  having the gap G that is smaller than that of the second position Z 2 , and a fourth maintenance surface  61   d  which maintains the position at a fourth position Z 4  having the gap G that is smaller than that of the third position Z 3 . A height difference L 3  between the first position Z 1  and the second position Z 2  in the first axis direction (the Z-axis direction) is larger than a height difference L 2  between the second position Z 2  and the third position Z 3  in the first axis direction. 
     In the stepped portion  63  illustrated in  FIGS.  6  to  8   , the first maintenance surface  61   a , a first adjustment surface  62   a , the second maintenance surface  61   b , a second adjustment surface  62   b , the third maintenance surface  61   c , a third adjustment surface  62   c , and the fourth maintenance surface  61   d  are arranged in this order from the left side when the drawings are viewed from the front side. 
     The cam member  60  is attached to the carriage  20  by an attachment portion that is provided on the upper side and is not illustrated, and regulates displacement in the Z-axis direction such that the cam member  60  is not separated from the carriage  20 . The cam member  60  is configured to be slidable in the X-axis direction that is the width direction without changing the position thereof in the Z-axis direction that is the first axis direction with respect to the carriage  20 . 
     The cam member  60  includes a guide pin  64  at the bottom thereof. The sliding member  50  includes a guide groove  54  formed in a shape corresponding to the stepped portion  63 . When the cam member  60  slides in the width direction, the guide pin  64  is guided to the guide groove  54  of the sliding member  50 . 
       FIG.  6    illustrates a state in which the contact portion  53  of the sliding member  50  is in contact with the fourth maintenance surface  61   d  of the stepped portion  63  of the cam member  60 , and a lower portion of the carriage  20  is located in the fourth position Z 4  in the Z-axis direction. 
     From the state of  FIG.  6   , as illustrated in  FIG.  7   , when the cam member  60  is slid in the +X direction so that the contact portion  53  of the sliding member  50  comes into contact with the first maintenance surface  61   a  of the stepped portion  63 , the carriage  20  is displaced in the Z-axis direction with respect to the sliding member  50  by a height difference L between the fourth maintenance surface  61   d  and the first maintenance surface  61   a , and the carriage  20  is located at the first position Z 1 . 
     As illustrated in  FIG.  8   , in the stepped portion  63 , L 1  denotes an interval between the first maintenance surface  61   a  and the second maintenance surface  61   b  as adjacent maintenance surfaces  61 , L 2  denotes an interval between the second maintenance surface  61   b  and the third maintenance surface  61   c  as adjacent maintenance surfaces  61 , and L 3  denotes an interval between the third maintenance surface  61   c  and the fourth maintenance surface  61   d  as adjacent maintenance surfaces  61 . 
     From the state illustrated in  FIG.  7   , that is, a state in which the contact portion  53  comes into contact with the first maintenance surface  61   a  so that the recording head  10  is located at the first position Z 1  in the Z-axis direction, when the cam member  60  is slid in the −X direction, the contact portion  53  can be guided by the first adjustment surface  62   a  and brought into contact with the second maintenance surface  61   b . At this time, the carriage  20  is displaced in the −Z direction, and the carriage  20  is located at the second position Z 2 . 
     Further, when the cam member  60  is slid in the −X direction, the contact portion  53  can be guided by the second adjustment surface  62   b  and can be brought into contact with the third maintenance surface  61   c . At this time, the carriage  20  is displaced in the −Z direction, and the carriage  20  is located at the third position Z 3 . 
     Further, when the cam member  60  is slid in the −X direction, the contact portion  53  can be guided by the third adjustment surface  62   c  and can be brought into contact with the fourth maintenance surface  61   d  as illustrated in  FIG.  6   . At this time, the carriage  20  is displaced in the −Z direction, and the carriage  20  is located at the fourth position Z 4 . The gap is the smallest when the carriage  20  is located at the fourth position Z 4 , and the gap is the largest when the carriage  20  is located at the first position Z 1 . 
     As described above, the gap adjustment unit  40  is configured to change a gap when the cam member  60  slides in the width direction (the X-axis direction) with respect to the carriage  20  and the sliding member  50 . 
     In the present embodiment, the gap adjustment unit  40  includes a buffer unit  70  that decreases a displacement speed of the carriage  20  in the first axis direction (the Z-axis direction) when the gap is reduced. In other words, the buffer unit  70  is provided to decrease the displacement speed of the carriage  20 , which is displaced in a direction in which the recording head  10  is positioned downward in the Z-axis direction from the first position Z 1  illustrated in  FIG.  7   . 
     Since the gap adjustment unit  40  includes the buffer unit  70 , the displacement speed of the carriage  20  that is displaced in a direction in which the gap is reduced can be reduced, and a sound that is generated when the carriage  20  is displaced can be suppressed. 
     In the present embodiment, the buffer unit  70  illustrated in  FIGS.  6  and  7    includes a rack and pinion mechanism constituted by a rack  71  and a pinion gear  72 . The rack  71  constituting the rack and pinion mechanism is provided in the sliding member  50  such that teeth are arranged in the first axis direction. The rack  71  has a lower end attached to the sliding member  50 . 
     The pinion gear  72  constituting the rack and pinion mechanism is provided in the carriage  20 . The buffer unit  70  is configured to reduce the displacement speed of the carriage  20  by applying resistance when the pinion gear  72  rotates. 
     Since the buffer unit  70  is configured in this manner, a structure of the buffer unit  70  can be simplified, and costs thereof can be reduced. 
     In the present embodiment, the buffer unit  70  is configured to impart resistance to the pinion gear  72  by a damper  73 . That is, the pinion gear  72  is configured as a gear damper including the damper  73 . By using the damper  73 , a simple configuration in which rotational resistance is applied to the pinion gear  72  can be achieved. 
     Further, the buffer unit  70  acts on the carriage  20  that is displaced in a direction including a vertical downward component, that is, the −Z direction, in the Z-axis direction that is the first axis direction, and does not act on the carriage  20  that is displaced in the direction including the vertical upward component, that is, the +Z direction, in the Z-axis direction. 
     In more detail, the pinion gear  72  is provided with a one-way clutch that is not illustrated. When the carriage  20  is displaced in the −Z direction, the pinion gear  72  rotates in a counterclockwise direction when  FIGS.  6  and  7    is viewed from the front side, and a buffering action by the damper  73  acts on the carriage  20 . In contrast, when the carriage  20  is displaced in the +Z direction, the pinion gear  72  is idled by the one-way clutch, and the buffering action by the damper  73  does not act on the carriage  20 . 
     With this configuration, when the carriage  20  is displaced downward, the carriage  20  is decelerated by the buffer unit  70 , and a possibility that the carriage  20  is vigorously displaced by a self-weight thereof to make a loud sound can be reduced. On the other hand, since the buffer unit  70  does not act when the carriage  20  is displaced upward, an increase in load when the carriage  20  is displaced upward can be suppressed. 
     Embodiment 2 
     In Embodiment 2, a gap adjustment unit  40 A including a buffer unit  70 A having a configuration that is different from that of Embodiment 1 will be described with reference to  FIGS.  9  and  10   . Description will be made also with reference to  FIG.  8    used in the description of Embodiment 1. 
     In the following embodiments, the same components as those of Embodiment 1 are denoted by the same reference numerals, and description of the components will be omitted. 
     In  FIG.  8   , the buffer unit  70 A acts when the gap G changes from a size defined by the first position Z 1  to a size defined by the second position Z 2 , and does not act when the gap G changes from the size defined by the second position Z 2  to a size defined by the third position Z 3 . 
     In more detail, the buffer unit  70 A illustrated in  FIGS.  9  and  10    includes a rack and pinion mechanism constituted by a rack  71 A and a pinion gear  72 . Similar to the buffer unit  70  of Embodiment 1, the pinion gear  72  is provided in the carriage  20 , and is configured to reduce the displacement speed of the carriage  20  by imparting resistance when the pinion gear  72  rotates. The pinion gear  72  is provided with the damper  73 . 
     The rack  71 A has teeth arranged in the first axis direction (the Z-axis direction) and is provided on the sliding member  50 . The rack  71 A is provided with teeth to engage with the pinion gear  72  from a state in which the contact portion  53  of the sliding member  50  is in contact with the first maintenance surface  61   a  of the stepped portion  63  as illustrated in  FIG.  9    to a state in which the contact portion  53  of the sliding member  50  is in contact with the second maintenance surface  61   b  of the stepped portion  63  as illustrated in  FIG.  10   . That is, when the carriage  20  is displaced from the first position Z 1  (see  FIG.  9   ) to the second position Z 2  (see  FIG.  10   ), the rack  71 A and the pinion gear  72  engage with each other. Thereafter, when the contact portion  53  of the sliding member  50  comes into contact with the fourth maintenance surface  61   d  through the third maintenance surface  61   c  from the second maintenance surface  61   b , the pinion gear  72  is disengaged from the rack  71 A. 
     As illustrated in  FIG.  8   , the height difference L 1  between the first maintenance surface  61   a  and the second maintenance surface  61   b  is larger than the height difference L 2  between the second maintenance surface  61   b  and the third maintenance surface  61   c  and the height difference L 3  between the third maintenance surface  61   c  and the fourth maintenance surface  61   d . Therefore, when the carriage  20  is displaced from the first position Z 1  to the second position Z 2 , the carriage  20  is displaced most downward, and large noise is likely to be generated. According to the present embodiment, only when a large sound is likely to be generated since the carriage  20  is displaced greatly downward, the buffer unit  70 A can act on the carriage  20 , so that generation of sound due to the displacement of the carriage  20  can be effectively suppressed. 
     Embodiment 3 
     In Embodiment 3, a gap adjustment unit  40 B including a buffer unit  70 B will be described with reference to  FIG.  11   . 
     The buffer unit  70 B illustrated in  FIG.  11    includes a first driven gear  74  as a driven gear that engages with the pinion gear  72  and is driven to rotate. The first driven gear  74  is a gear having a larger number of teeth than that of the pinion gear  72 , and a reduction gear ratio when power is transmitted from the pinion gear  72  to the first driven gear  74  is larger than 1. Similarly, the buffer unit  70 B includes a second driven gear  75  that engages with the first driven gear  74  and is driven to rotate. The second driven gear  75  is a gear having a larger number of teeth than that of the first driven gear  74 , and a reduction gear ratio when power is transmitted from the first driven gear  74  to the second driven gear  75  is larger than 1. Thus, a reduction gear ratio when power is transmitted from the pinion gear  72  to the second driven gear  75  is larger than 1. As a result, the pinion gear  72  is configured to receive resistance during rotation. 
     In the present embodiment, by using the buffer unit  70 B having the above-described configuration, a configuration can be simply achieved that rotational resistance is applied to the pinion gear  72 . 
     Embodiment 4 
     In Embodiment 4, a gap adjustment unit  40 C including a buffer unit  70 C will be described with reference to  FIG.  12   . 
     The buffer unit  70 C illustrated in  FIG.  12    includes a spring member  76  as an elastic member, which is provided between the sliding member  50  and the carriage  20 , and the displacement speed of the carriage  20  is reduced by elasticity of the spring member  76 . 
     The spring member  76  is a tension spring provided between a first hook  55  provided in the sliding member  50  and a second hook  29  provided in the carriage  20 . Since the carriage  20  is displaced downward against a spring force of the spring member  76 , the displacement speed of the carriage  20  to the lower side can be reduced, and generation of a sound at this time can be suppressed. 
     Embodiment 5 
     In Embodiment 5, a gap adjustment unit  40 D will be described with reference to  FIG.  13   . 
     In the gap adjustment unit  40 D, similar to the cam member  60  of Embodiment 1, the stepped portion  63  of the cam member  60  has, as the maintenance surfaces  61 , the first maintenance surface  61   a , the second maintenance surface  61   b , the third maintenance surface  61   c , and the fourth maintenance surface  61   d . The height difference L 1  between the first position Z 1  and the second position Z 2  in the first axis direction (the Z-axis direction) is larger than the height difference L 2  between the second position Z 2  and the third position Z 3  in the first axis direction. An inclination angle α 1  of the first adjustment surface  62   a  coupling the first maintenance surface  61   a  and the second maintenance surface  61   b  with respect to a horizontal plane is larger than an inclination angle α 2  of the second adjustment surface  62   b  coupling the second maintenance surface  61   b  and the third maintenance surface  61   c  with respect to the horizontal plane. In the present embodiment, the inclination angle α 1  is smaller than an inclination angle α 3  of the third adjustment surface  62   c  coupling the third maintenance surface  61   c  and the fourth maintenance surface  61   d  with respect to the horizontal plane. Further, the inclination angle α 2  and the inclination angle α 3  are set to the same angle. 
     In the stepped portion  63 , since the inclination angle α 1  of the first adjustment surface  62   a  used when the carriage  20  is displaced in the Z-axis direction by L 1  is smaller than the inclination angle α 2  of the second adjustment surface  62   b  used when the carriage  20  is displaced by L 2  that is smaller than L 1 , an inclination of the first adjustment surface  62   a  used when the carriage  20  is displaced more greatly can be made gentle, and a sound generated when the carriage  20  is displaced can be reduced. In the present embodiment, the buffer unit for reducing the displacement speed of the carriage  20  to the lower side can be omitted. 
     Embodiment 6 
     In Embodiment 6, a gap adjustment unit  40 E including the buffer unit  70 D will be described with reference to  FIGS.  20  and  21   . A cam member  60 A provided in the gap adjustment unit  40 E has the same configuration except that a rack  71 B is integrally provided as compared to the cam member  60  described in Embodiment 1. In  FIGS.  20  and  21   , in order to avoid complication of the drawing, reference numerals of the adjustment surface  62  illustrated in Embodiment 1 will be omitted, and only necessary reference numerals will be illustrated for the maintenance surface  61 . 
       FIG.  20    illustrates a state in which the position of the carriage  20  is in the first position Z 1  where the gap G (see  FIG.  8   ) is the largest, and  FIG.  21    illustrates a state in which the position of the carriage  20  is in the fourth position Z 4  where the gap G (see  FIG.  8   ) is the smallest. 
     In  FIGS.  20  and  21   , the buffer unit  70 D includes a rack and pinion mechanism including the rack  71 B and the pinion gear  72 . Unlike Embodiment 1, the rack  71 B constituting the rack and pinion mechanism is provided integrally with the cam member  60 A such that teeth are arranged in the X-axis direction. 
     The pinion gear  72  constituting the rack and pinion mechanism is provided in the carriage  20 . The pinion gear  72  engages with the damper gear  73   a . The damper gear  73   a  is a gear provided integrally with the damper  73 . 
     With this configuration, the displacement speed of the carriage  20  to which resistance is applied when the pinion gear  72  rotates is reduced. 
     Further, in contrast to Embodiment 1, in the present embodiment, the length of the rack  71 B can be increased, and the amount of rotation of the pinion gear  72  can be further ensured. Therefore, influence of a backlash in meshing of gears can be reduced, and the sound generated when the carriage  20  is displaced can be suppressed more reliably. 
     Further, in the present embodiment, the buffer unit  70 D is provided in the carriage  20  in a direction opposite to the home position. In  FIGS.  20  and  21   , a position CL is a central position of the carriage  20  in the X-axis direction, the −X direction is a direction of the home position of the carriage  20  and the +X direction is a direction that is opposite to the direction of the home position. The buffer unit  70 D is provided in the +X direction with respect to the position CL. 
     Here, when the buffer unit  70 D is hypothetically provided in the −X direction with respect to the position CL, the pinion gear  72  is disengaged from the rack  71 B when the cam member  60 A is displaced in the +X direction. Thus, the cam member  60 A needs to be extended in the −X direction, and the apparatus becomes large. The cam member  60 A is displaced from a central area of the carriage  20  as illustrated in  FIG.  21    to an area of the carriage  20  in the +X direction as illustrated in  FIG.  20    and is displaced in an opposite direction thereto. That is, the cam member  60 A is displaced in an area in the +X direction with respect to the central position CL of the carriage  20  in the X-axis direction. 
     However, as described above, since the buffer unit  70 D is provided in the carriage  20  in the direction opposite to the home position, an increase in the size of the apparatus can be suppressed. 
     Even in such a buffer unit  70 D, when the one-way clutch is provided, it can be configured such that a buffering action is generated on the carriage  20  that displaces in a direction including a vertical downward component, that is, the −Z direction, in the Z-axis direction that is the first axis direction, and that the buffering action is not generated on the carriage  20  that displaces in the direction including the vertical upward component, that is, the +Z direction, in the Z-axis direction. 
     Modification Example of Gap Adjustment Unit 
     A modification example of the gap adjustment unit  40  will be described with reference to  FIGS.  14  to  17   . The gap adjustment unit  40  can be provided with auxiliary adjustment units  80 . As illustrated in  FIG.  14   , the auxiliary adjustment units  80  are provided on the carriage  20 , and are arranged on both sides in the width direction on the upper side of the sliding member  50 . 
     As illustrated in  FIG.  15   , the auxiliary adjustment unit  80  includes a cam  81  that can pivot about a shaft portion  84  provided in the carriage  20 . An abutting portion  56  on which the cam  81  can abut is provided at the upper portion of the sliding member  50 . 
     The cam  81  includes an arc-shaped portion  81   a  and a flat-shaped portion  81   b . The arc-shaped portion  81   a  is a portion that is in contact with the abutting portion  56  in  FIG.  15   , and is formed in a shape along a circular arc with the shaft portion  84  as a center. The flat-shaped portion  81   b  is formed in a flat shape corresponding to a string obtained by cutting a part of a circle with the shaft portion  84  as a center. Since a distance from the shaft portion  84  to the flat-shaped portion  81   b  is shorter than a distance from the shaft portion  84  to the arc-shaped portion  81   a , the cam  81  is pivoted to switch between a state (see  FIG.  15   ) in which the arc-shaped portion  81   a  abuts on the abutting portion  56  of the sliding member  50  and a state (not illustrated) in which the flat-shaped portion  81   b  abuts on the abutting portion  56  of the sliding member  50 , so that a relative position of the carriage  20  with respect to the sliding member  50  can be changed. 
     As illustrated in  FIG.  15   , the cam  81  includes a regulation groove  82  provided along a pivot direction of the cam  81 , and a screw  83  is attached to the carriage  20  while being inserted into the regulation groove  82 . With this configuration, the pivot of the cam  81  is regulated within a range in which the screw  83  is guided by the regulation groove  82 . 
     Further, the auxiliary adjustment unit  80  can be adjusted when the carriage  20  is located at the fourth position Z 4 , that is, only when the carriage  20  is located at the lowermost adjustment position by the gap adjustment unit  40 . 
     In detail, as illustrated in  FIG.  16   , when the contact portion  53  provided in the sliding member  50  comes into contact with the fourth maintenance surface  61   d  of the stepped portion  63  of the cam member  60  so that the carriage  20  is located at the fourth position Z 4 , the cam  81  of the auxiliary adjustment unit  80  can come into contact with the abutting portion  56  at the upper portion of the sliding member  50 . When the contact portion  53  comes into contact with another maintenance surface  61 , that is, the first maintenance surface  61   a , the second maintenance surface  61   b , and the third maintenance surface  61   c  so that the carriage  20  is located at the first position Z 1  to the third position Z 3 , the cam  81  is not in contact with the abutting portion  56  at the upper portion of the sliding member  50 . 
       FIG.  17    illustrates a state in which the contact portion  53  is in contact with the fourth maintenance surface  61   d  and the carriage  20  is located at the fourth position Z 4 . At this time, the cam  81  is separated from the abutting portion  56 . 
     With the above configuration, in a state in which the carriage  20  is located at the fourth position Z 4 , fine adjustment in the Z-axis direction can be performed by the auxiliary adjustment unit  80 . 
     The auxiliary adjustment unit  80  may be provided in the gap adjustment units  40 A to  40 E described in Embodiment 2 to Embodiment 6. 
     Another Example of Unit for Adjusting Position of Carriage 
     The position of the carriage  20  in the first axis direction (the Z-axis direction) can also be adjusted by a configuration illustrated in  FIGS.  18  and  19   . A sliding member  90  that moves in the width direction integrally with the carriage  20  while sliding against the guide member  28  (see  FIG.  3   ) is fixed to the carriage  20  illustrated in  FIGS.  18  and  19   . That is, a relative position between the carriage  20  and the sliding member  90  is not changed. 
     In  FIG.  18   , a support member  98  is provided on a side surface of the sliding member  90  in the −X direction. The support member  98  is provided with a bearing that is not illustrated, and has a shaft  95  pivotably attached thereto to extend in the X-axis direction which is the width direction. A pivot shaft  94  of a fan-shaped member  91  is fixed to an end portion of the shaft  95  in the −X direction. By pivoting the fan-shaped member  91 , the shaft  95  can be pivoted. 
     The fan-shaped member  91  includes a regulation groove  92  provided along a pivot direction of the fan-shaped member  91 , and a screw  93  is attached to the support member  98  while being inserted into the regulation groove  92 . With this configuration, the pivot of the fan-shaped member  91  is regulated within a range in which the screw  93  is guided by the regulation groove  92 . 
     The shaft  95  is provided with an eccentric cam  96  illustrated in  FIG.  19   . The eccentric cam  96  includes a thick portion  96   a  that is thick with respect to the shaft  95  and a thin portion  96   b  that is thin with respect to the shaft  95 . An abutting portion  97  that can contact the eccentric cam  96  is provided at a lower portion of the sliding member  90 . 
     When the fan-shaped member  91  pivots, the shaft  95  pivots, so that the position of the eccentric cam  96  that is in contact with the abutting portion  97  of the sliding member  90  is switched between the thick portion  96   a  and the thin portion  96   b . Thus, the height of the carriage  20  can be changed.