Abstract:
A recording apparatus includes a tray in which a recording material is to be set, the tray being reciprocated between a first position where the tray is exposed to allow the recording material to be set therein and a second position shifted from the first position in a first direction, where the tray is stored; a transporting mechanism that applies transportation force for reciprocating the tray; and a transportation-force transmitting member that is connected to the tray to mediate transmission of the transportation force to the tray and is capable of increasing or decreasing a space occupied by the transportation-force transmitting member in the direction of reciprocation.

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to recording apparatuses, such as printers, facsimiles, or copiers, including multi-function apparatuses, having a tray accommodated in a main body of the recording apparatus. A recording material on which recording is performed, such as an optical disc, can be set in the tray. 
     2. Related Art 
     An ink jet printer as an example of a recording apparatus will be described below. Some ink jet printers can selectively perform recording on both soft recording materials that do not stand on their own, such as sheets or films, and hard recording materials that stand on their own, such as optical discs (CD-Rs, DVD-Rs, and the like). When recording is to be performed on a recording material such as a CD-R, a dedicated tray that is separately provided as an accessory is used, or, as disclosed in Japanese Unexamined Patent Application Publication No. 2005-59584, an ink jet printer having a tray accommodated in the main body of the printer is used. The tray has a setting recess in which a recording material, such as a CD-R, is set. 
     However, because such a printer having a built-in tray reciprocates the tray over a wide area between a set position and a stored position, it uses a long tray having a great length in the direction in which the tray reciprocates (hereinafter, “depth”). A great depth of the tray increases the depth of the main body of the printer, making it difficult to reduce the size of the main body of the recording apparatus. 
     SUMMARY 
     An advantage of some aspects of the invention is that it provides a recording apparatus that enables the use of a short tray having a small depth to reduce the size of a main body of the recording apparatus. 
     According to a first aspect of the invention, a recording apparatus includes a holding tray accommodated in a main body of the recording apparatus, in which a recording material can be set; a reciprocation path extending between a set position and a stored position of the holding tray and guides the holding tray reciprocating therebetween; a transporting mechanism provided in the reciprocation path, which transports the holding tray; and a recording execution unit that performs recording on the recording material transported to a recording execution area. The holding tray is formed so as to be shorter than the moving distance over which it reciprocates, and has an extendable moving mechanism that enables the holding tray to move over the moving distance. 
     According to this embodiment, the use of the extendable moving mechanism enables the use of a short holding tray formed so as to be shorter than the entire moving distance over which the holding tray reciprocates. This enables the short holding tray to be moved from the stored position at the back of the main body of the recording apparatus to the set position at the front of the main body of the recording apparatus over a large stroke. This can reduce the size of recording apparatuses having a holding tray accommodated therein. 
     According to a second aspect of the invention, in the recording apparatus according to the first aspect, the extendable moving mechanism includes a guide arm connected to an end of the holding tray so as to change the inclination thereof with respect to the direction of reciprocation of the holding tray, and a guide portion engaged with the guide arm to guide the guide arm to change the inclination and move. 
     According to this embodiment, the use of the guide rail and the guide arm capable of changing its inclination enables the guide arm to be folded and stored along the rear end of the holding tray when the holding tray is located at the stored position. On the other hand, when the holding tray is moved to the set position, the guide arm extends straight in the conveying direction. Furthermore, the extendable moving mechanism consisting of a small number of components can be formed with a relatively simple structure. 
     According to a third aspect of the invention, in the recording apparatus according to the second aspect, the guide arm includes a plurality of guide arms, and the plurality of guide arms overlie each other when the holding tray is located at the stored position. 
     According to this embodiment, the provision of the plurality of guide arms stabilizes the orientation of the holding tray during transportation and enables accurate and smooth transportation of the recording material. Furthermore, by storing the plurality of guide arms so as to overlie each other when the holding tray is located at the stored position, the size of the main body of the recording apparatus in a depth direction can be further reduced. In addition, by providing the guide arms with engaging step portions, the guide arms, when they overlie each other, have a thickness equivalent to one guide arm. This reduces the height of the main body of the recording apparatus. 
     According to a fourth aspect of the invention, in the recording apparatus according to the second or third aspect, the guide portion is provided in one or both of path-forming members disposed so as to face each other to form the reciprocation path. In the case where a plurality of guide portions are provided, one of the guide arms is engaged with the guide portion in one of the path-forming members, and the other of the guide arm is engaged with the guide portion in the other of the path-forming members. 
     According to this embodiment, because the guide portion is formed using the existing path-forming members, the number of components is reduced. Furthermore, for example, by engaging the upper guide arm (one of the guide arms) with the guide portion in the upper path-forming member (one of the path-forming members) and by engaging the lower guide arm (the other one of the guide arms) with the guide portion in the lower path-forming member (the other one of the path-forming members), the guide arms are efficiently arranged while preventing interference between the guide arms and reducing the height of the main body of the recording apparatus. 
     According to a fifth aspect of the invention, in the recording apparatus according to any one of the second to fourth aspects, when the recording material moves between the recording termination position in the recording execution area and the set position, the holding tray is transported by the guide arm that receives transportation force from the transporting mechanism. 
     According to this embodiment, by using the guide arm as a transportation-force transmitting member for applying transportation force to the holding tray, a long movement stroke can be achieved even when a short holding tray is used. 
     According to a sixth aspect of the invention, in the recording apparatus according to the fifth aspect, a surface of the guide arm to be in contact with a transportation driving roller constituting the transporting mechanism, at least in an area which receives transportation force from the transporting mechanism, is formed in a flat surface. 
     According to this embodiment, in a moving area where the guide arm functions as the transportation-force transmitting member, a contact surface of the guide arm to be in contact with the transportation driving roller is formed in a flat surface having no step portion. Thus, smooth transportation of the holding tray in the moving area is achieved. 
     According to a seventh aspect of the invention, in the recording apparatus according to any one of the second to sixth aspects, when the guide arm includes a plurality of guide arms, the positional relationship between the holding tray and the guide arm at one connection portion of the holding tray and the guide arm is different from that at the other connection portion. 
     There are slight steps at the connection portions of the holding tray and the guide arms even if they are designed and formed to be flush with each other. According to this embodiment, because the positional relationship between the holding tray and the guide arm at one connection portion is different from that at the other connection portion, the steps are compensated for and thus exert almost no influence. That is, the influence of the steps on transportation of the holding tray can be reduced. 
     According to an eighth aspect of the invention, in the recording apparatus according to any one of the second to seventh aspects, the guide arm has, at its base end, an engaging portion to be engaged with the guide portion and a retaining portion for preventing the engaging portion from coming off the guide portion when the tray is moved to the set position. 
     According to this embodiment, the retaining portion for preventing the engaging portion provided on the guide arm from coming off the guide portion when the holding tray is moved from the stored position to the set position and stopped. Thus, even if unexpected external force is applied to the holding tray or the guide arm, the guide arm does not come off the guide portion. As a result, the holding tray does not come off the recording apparatus. 
     According to a ninth aspect of the invention, in the recording apparatus according to any one of the first to sixth aspect, when the holding tray moves between the recording start position and the recording termination position, the holding tray receives transportation force from the transporting mechanism. 
     According to this embodiment, the transporting mechanism directly applies transportation force to the holding tray in the area between the recording start position to the recording termination position, where recording is performed on the recording surface of the recording material. Thus, the orientation of the recording material during transportation is stabilized, and smooth transportation of the recording material is achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a perspective view showing the internal structure of an ink jet printer according to this embodiment. 
         FIG. 2  is a side sectional view of the ink jet printer when a tray is stored. 
         FIG. 3  is a side sectional view of the ink jet printer when recording is started. 
         FIG. 4  is a side sectional view of the ink jet printer when the tray is located at a recording termination position. 
         FIG. 5  is a side sectional view of the ink jet printer when a hard recording material is set. 
         FIG. 6  is a plan view of an extendable moving mechanism when the tray is stored. 
         FIG. 7  is a sectional view taken along line VII-VII in  FIG. 6 . 
         FIG. 8  is a plan view of the extendable moving mechanism when the hard recording material is set. 
         FIG. 9  is a sectional view taken along line IX-IX in  FIG. 8 , showing a plurality of positions of the tray. 
         FIG. 10  is an exploded perspective view showing connection structures of the tray and arms. 
         FIG. 11  is a perspective view of the extendable moving mechanism when the tray is stored. 
         FIG. 12  is a bottom view of an upper-path forming member. 
         FIG. 13  is a plan view of a recording-medium transportation unit when the tray is stored. 
         FIG. 14  is a plan view of the ink jet printer when recording is started. 
         FIG. 15  is a plan view of the ink jet printer when the tray is located at a recording termination position. 
         FIG. 16  is a plan view of the ink jet printer when the hard recording material is set. 
         FIG. 17  is a plan view of another embodiment, in which the structure of the extendable moving mechanism is changed. 
         FIGS. 18A and 18B  are side views of another embodiment when the tray is stored and when the hard recording material is set, respectively. 
         FIG. 19  is an enlarged perspective view of the vicinity of a guide pin, in which a base end of the arm is viewed from diagonally above. 
         FIG. 20  is a perspective view of the upper-path forming member viewed from diagonally above, in which a part of the tip of a guide rail to be engaged with the guide pin provided on the arm is enlarged. 
         FIG. 21  is a perspective view of the upper-path forming member viewed from diagonally below, in which a part of an end of the guide rail to be engaged with the guide pin provided on the arm is enlarged. 
         FIG. 22  is a perspective view showing the relationship between the arm and the guide rail immediately before the arm is fully extended. 
         FIG. 23  is an enlarged perspective view of the vicinity of the base end and the guide pin, when the arm is turned upside-down. 
         FIG. 24  is a perspective view of a lower-path forming member viewed from diagonally above, in which a part of an end of the guide rail to be engaged with the guide pin provided on the arm is enlarged. 
         FIG. 25  is a perspective view of a lower-path forming member viewed from diagonally below, in which a part of an end of the guide rail to be engaged with the guide pin provided on the arm is enlarged. 
         FIG. 26  is a perspective view showing the relationship between the arm and the guide rail immediately before the arm is fully extended. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A recording apparatus including a recording-medium transportation unit of the invention will be described below. First, an outline of the overall structure of an ink jet printer  1  as a preferable embodiment of the recording apparatus of the invention will be described with reference to the drawings. 
       FIG. 1  is a perspective view showing the internal structure of an ink jet printer, and  FIG. 2  is a side sectional view showing the schematic internal structure of the ink jet printer when a tray is located at a stored position.  FIG. 3  is a side sectional view of the ink jet printer when the tray is located at a recording start position, and  FIG. 4  is a side sectional view of the ink jet printer when the tray is located at a recording termination position.  FIG. 5  is a side sectional view of the ink jet printer when the tray is located at a set position. 
     The ink jet printer  1  illustrated in the drawings is a multi-function ink jet printer having an image-reading apparatus (scanner, not shown) mounted thereon. The ink jet printer  1  can perform recording on both soft recording materials P, such as sheets or films, and hard recording materials Q, such as optical discs including CD-Rs and DVD-Rs. In addition, the ink jet printer  1  is a serial printer having a recording head  42  on the bottom surface of a carriage  40  that can reciprocate in a width direction B perpendicular to a conveying direction A in the recording execution area of the above-mentioned two types of media, namely, the soft recording materials P and the hard recording materials Q. 
     The ink jet printer  1  includes a rectangular-parallelepiped-shaped printer main body  2 , serving as a main body of the recording apparatus, with an exterior consisting of relatively flat surfaces. The printer main body  2  has a feeding cassette  11  that can store multiple soft recording materials P such as normal sheets in a stacked state and that is removably fitted to a lower central portion of a front surface  2   a . A discharging stacker  47 , on which the soft recording materials P after recording are stacked, is provided above the surface to which the feeding cassette  11  is fitted. In addition, the front surface  2   a  of the printer main body  2  has operation buttons (not shown) for executing various operation instructions, a cartridge holder (not shown) for accommodating ink cartridges, etc. 
     The feeding cassette  11  is provided at a start position of a transportation path of the soft recording materials P. The soft recording materials P stored in the feeding cassette  11  are fed on a piece-by-piece basis from the top by an auto feeder  3  to a U-shaped reversing path  50  described below. The auto feeder  3  includes a pick-up roller  16  that draws upper soft recording materials P in the feeding cassette  11  backwards, a separating slope  12  that preliminarily separates these upper soft recording materials P and guides them to the U-shaped reversing path  50 , a first guide roller  20  provided so as to be freely rotatable at a position diagonally behind and above the separating slope  12 , and separating rollers  21  provided at a position diagonally behind and above the first guide roller  20 . 
     The pick-up roller  16  is provided at an end of a swing arm  17  that swings about a swing shaft  18 . The pick-up roller  16  is pressed against the top surface of the soft recording material P and is rotated in the conveying direction A during feeding. Thus, the upper soft recording materials P in the feeding cassette  11  can be drawn backwards. The separating rollers  21  include a pair of nip rollers, namely, a separating driven roller  22  provided with a torque limiter and a separating driving roller  23 . The separating rollers  21  perform main separation to completely separate the uppermost soft recording material P from the subsequent soft recording materials P that cannot be separated in the preliminary separation by the separating slope  12 . 
     The soft recording material P fed by the auto feeder  3  is transported in the U-shaped reversing path  50  to a recording position  51 . Below the recording position  51  is provided a platen  38  that supports the bottom surface of the transported soft recording material P or the tray (holding the hard recording material Q) and that defines a gap PG between itself and the bottom surface of the recording head  42 . The platen  38  includes a transportation guide portion  39  serving as a support member, a platen rib  38   a  formed on the top surface of the transportation guide portion  39 , and an ink collecting groove  39   a  for collecting excess ink not used in recording. 
     Above the recording position  51  are provided the recording head  42  serving as a main component of the recording execution unit  4  and a carriage  40  that has the recording head  42  on the bottom surface thereof and can reciprocate in the width direction B so as to be guided by a carriage guide shaft  41 . Furthermore, the recording execution unit  4  includes a plurality of ink tubes and ink supply pumps (not shown) for supplying ink of different colors to the recording head  42 , a capping device (not shown) provided at a home position of the carriage  40 , and an auto gap-adjusting mechanism (not shown) that is used when the soft recording material P and the hard recording material Q are switched. 
     A recording-material discharge unit  6  is provided downstream of the recording position  51  in the conveying direction A. The recording-material discharge unit  6  includes discharge rollers  43  consisting of a pair of nip rollers, namely, a discharging driving roller  44  and a discharging driven roller  45 , and the discharging stacker  47 . The discharging stacker  47  has an extendable stacker  48  nested therein. 
     First Embodiment 
     A recording apparatus having the recording-medium transportation unit  5  according to this embodiment, which is applied to the ink jet printer  1  having the above-described structure, will be described in detail with reference to the drawings. 
       FIG. 6  is a plan view of the extendable moving mechanism when the tray is located at the stored position.  FIG. 7  is a sectional view taken along line VII-VII in  FIG. 6 .  FIG. 8  is a plan view of the extendable moving mechanism when the tray is located at the set position.  FIG. 9  is a sectional view taken along line IX-IX in  FIG. 8 , showing a plurality of positions of the tray.  FIG. 10  is an exploded perspective view of the tray and arms.  FIG. 11  is a perspective view when the tray is located at the stored position, viewed from diagonally above and behind.  FIG. 12  is a bottom view of the upper-path forming member. 
       FIG. 13  is a plan view showing the operation of the tray and the extendable moving mechanism, when the tray is located at the stored position.  FIG. 14  is a plan view when the tray is located at a recording start position.  FIG. 15  is a plan view when the tray is located at a recording termination position.  FIG. 16  is a plan view when the tray is located at the set position. 
     The recording-medium transportation unit  5  according to this embodiment basically includes: a short tray  55  accommodated in the printer main body  2 , in which a hard recording material Q, such as a CD-R, is to be set; a reciprocation path  56  that guides the tray  55  reciprocating between the set position  53  and the stored position  54 ; transportation rollers  34 , serving as a transporting mechanism, which are provided in the middle of the reciprocation path  56  and consist of a transportation driving roller  35  and a transportation driven roller  36  for applying transportation force to the tray  55 ; and an extendable moving mechanism  59  that is connected to the rear end of the tray  55  and has an extension function with a movement stroke S that enables the movement of the tray  55  between the set position  53  and the stored position  54 . 
     In addition to the above-described structures, the recording-medium transportation unit  5  according to this embodiment includes: the feeding cassette  11  that can store multiple soft recording materials P, such as normal sheets, in a stacked state; the U-shaped reversing path  50  that feeds the soft recording material P backwards from the feeding cassette  11 , causes it to make a U-turn, and guides it toward the front surface  2   a  of the printer main body  2 ; and an auxiliary transportation mechanism  67  that performs auxiliary transportation until the tray  55  is transferred to the transportation rollers  34 . 
     Herein, the term “the recording position  51 ” refers to a recording execution area in which the recording head  42  performs recording on a recording material. In  FIGS. 3 and 14 , reference numeral  60  denotes a front end position of the tray  55  when the recording on the hard recording material Q is started. This position will be referred to as a recording start position  60  of the tray  55 . Corresponding to the recording start position  60 , the front end position of the tray  55  when the recording on the hard recording material Q is terminated constitutes the recording termination position of the tray  55 . In  FIGS. 4 and 15 , reference numeral  61  denotes the front end position of the tray  55  at the recording termination position. 
     First, the U-shaped reversing path  50  constituting the transportation path for the soft recording material P will be described. The U-shaped reversing path  50  is provided in a rear space of the printer main body  2 . The U-shaped reversing path  50  is formed of, for example, two separate upper housings  63  and  64 , a transportation guide  37 , and a lower housing  65 , which constitute an outer guide surface  50   a  of the U-shaped reversing path  50 ; and the upper-path forming member  57 , which constitutes an inner guide surface  50   b  of the U-shaped reversing path  50 . 
     As shown in  FIGS. 2 to 4 , the U-shaped reversing path  50  includes: first intermediate feeding rollers  25  consisting of a pair of nip rollers, namely, a feeding driving roller  26  and a feeding driven roller  27 ; a freely rotatable second guide roller  29 ; and second intermediate feeding rollers  31  consisting of a pair of nip rollers, namely, a feeding driving roller  32  and a feeding driven roller  33 . Because of the feeding and guiding operations of the first intermediate feeding rollers  25 , the second guide roller  29 , and the second intermediate feeding rollers  31 , the soft recording material P fed to the U-shaped reversing path  50  passes through the U-shaped reversing path  50  and is fed to the nip point of the transportation rollers  34  provided near the downstream of the U-shaped reversing path  50 . 
     The transportation rollers  34  consist of a pair of nip rollers, namely, the transportation driving roller  35  supported by a roller driving shaft  35   a  and the transportation driven roller  36  provided so as to be freely rotatable at an end of the transportation guide  37 . The transportation driven roller  36  is located slightly downstream of the transportation driving roller  35  in the conveying direction A. By using the transportation rollers  34  consisting of the rollers arranged in this manner, the front end of the soft recording material P is pressed against the underlying platen rib  38   a  and is thereby prevented from touching the head. Thus, the recording quality is improved. 
     The roller driving shaft  35   a  receives motive power transmitted from a driving motor (not shown) to transport the soft recording material P and the tray  55  (hard recording material Q) and transmits the motive power via the gear train  66  to the auxiliary transportation mechanism  67  to perform movement starting operation to move the tray  55  from the stored position  54  and movement terminating operation to return the tray  55  to the stored position  54 . 
     In addition, the roller driving shaft  35   a  has a clutch device (not shown). By appropriately changing the engaging position of the clutch device, motive power of the roller driving shaft  35   a  can be selectively transmitted to the above-mentioned ink supply pumps (not shown), capping device, auto gap-adjusting mechanism, and auto feeder  3 . 
     The tray  55  is formed so as to be shorter than the entire moving distance over which it reciprocates. That is, the tray  55  is, as shown in  FIG. 10 , a short rectangular plate-like member having a small depth. A setting recess  71  in which the hard recording material Q is to be set is provided in the top surface  55   a  of the tray  55 , at the center in the width direction and slightly frontward, and a holding projection  72  for holding the hard recording material Q, provided at the center of the setting recess  71 . The hard recording materials Q that can be set in the tray  55  include various optical discs, such as CD-Rs, CD-RWs, DVD-Rs, DVD-RWs, blu-ray discs, which draw attention as a next-generation optical disc, and other discs to be developed, with a diameter of either 12 cm or 8 cm. 
     As shown in  FIG. 10 , a front end portion  80  of the tray  55  is formed in a comb-like zigzag shape, and projected portions thereof constitute guide nails  84  that are sloped toward the front edge. The tray  55 , near the left and right rear corners, has tongue-like connecting pieces  75 L and  75 R that are connected respectively to tips  74   a  and  74   a  of left and right arms  74 L and  74 R of the extendable moving mechanism  59  (described below) so as to be rotatable. The bottom surface of the connecting piece  75 L on the left side and the top surface of the connecting piece  75 R on the right side are provided with mushroom-shaped connecting projections  75   a  each having an engaging flange portion  85  at the tip. The connecting projections  75   a  will be engaged with left and right connecting holes  78 L and  78 R (described below). 
     The reciprocation path  56  includes the lower-path forming member  62  that supports the bottom surface  55   b  of the tray  55  when the tray  55  is located at the stored position  54 , left and right edge guides  76 L and  76 R for guiding the tray  55 , along which the left and right edges of the tray  55  slide, the transportation guide portion  39  that faces the bottom surface  55   b  of the tray  55  when the tray  55  is located at the recording position  51 , and the discharging stacker  47  that supports the bottom surface  55   b  of the tray  55  when the tray  55  is located at the set position  53 . 
     The lower-path forming member  62  is a short plate-like member having substantially the same size as the tray  55 . The left and right edge guides  76 L and  76 R are provided so as to extend upright from the left and right side edges of the lower-path forming member  62 . As shown in  FIGS. 10 and 15 , the lower-path forming member  62  has a guide rail  77 R engraved therein, having an L shape in plan view and serving as a guide portion, which is to be engaged with the guide pin  79  provided at the base end  74   b  of the right arm  74 R of the extendable moving mechanism  59  described below. 
     The extendable moving mechanism  59  includes the pair of left and right arms  74 L and  74 R connected to the rear edge of the tray  55  so as to be rotatable, and the guide rails  77 L and  77 R that serve as the left and right guide portions and engage with guide pins  79  and  79  provided at base ends  74   b  and  74   b  ( FIG. 9 ) of the arms  74 L and  74 R to guide the orientation and movement of the arms  74 L and  74 R. 
     The arms  74 L and  74 R are narrow, long plate-like members with rounded tips  74   a  and  74   a . The arms  74 L and  74 R are each formed such that the tip  74   a  and the base end  74   b  are different in shape, i.e., the tip  74   a  is wide and thick and the base end  74   b  is narrow and thin. By overlaying the thin portions of the left and right arms  74 L and  74 R on top of each other, the left and right arms  74 L and  74 R can be stored in a compact, folded state without increasing the thickness or causing interference with each other. In this embodiment, the left arm  74 L is positioned above the right arm  74 R at the position where the left and right arms  74 L and  74 R overlie each other. 
     The tip  74   a  of the left arm  74 L has a stepped shape in which the top surface is lowered, and has, at the center thereof, an elongated connecting hole  78  that receives the downwardly projecting connecting projection  75   a  of the connecting piece  75 L provided at the rear edge, on the left side, of the tray  55 . On the other hand, the tip  74   a  of the right arm  74 R has a stepped shape in which the bottom surface is lowered, and has, at the center thereof, an elongated connecting hole  78 R that receives the upwardly projecting connecting projection  75   a  of the connecting piece  75 R provided at the rear edge, on the right side, of the tray  55 . The connecting projections  75   a  and  75   a  are formed so as not to project from the corresponding connecting holes  78 L and  78 R when the connecting pieces  75 L and  75 R are connected to the tips  74   a  and  74   a  of the arms  74 L and  74 R, respectively. 
     Thus, the tray  55  and the pair of left and right arms  74 L and  74 R are formed to have a substantially uniform thickness in the area where they are to be in contact with the transportation rollers  34 . In particular, when the tray  55  moves between the recording termination position and the set position  53 , the arms  74 L and  74 R are held between the transportation rollers  34  so that the transportation force is applied to the tray  55  via the arms  74 L and  74 R. Thus, in the above-mentioned moving area, contact surfaces  86 L and  86 R of the arms  74 L and  74 R on the transportation rollers  34  side are flat surfaces. 
     There is a slight step due to fabrication error or assembly error at each of the connection portion  87 L on the left side (in  FIG. 10 ) of the tray  55 , at which the connecting piece  75 L and the arm  74 L are connected, and the connection portion  87 R on the right side of the tray  55 , at which the connecting piece  75 R and the arm  74 R are connected. However, because the positional relationship in the top-bottom direction between the tray  55  and the arm  74 L of the left connection portion  87 L is opposite to that between the tray  55  and the arm  74 R of the right connection portion  87 R, these steps at the left and right connection portions  87 L and  87 R are located at different positions in the conveying direction. Accordingly, when the connection portions  87 L and  87 R pass through the nip between the transportation rollers  34 , the steps at the left and right connection portions  87 L and  87 R successively pass through the nip between the transportation rollers  34 . Thus, the tray  55  is smoothly transported regardless of whether it is transported in the conveying direction A or returning direction D. 
     The guide rails  77 L and  77 R, serving as guide portions, are grooves arranged symmetrically and each having an L shape in plan view. The left guide rail  77 L is provided in an inner surface  57   a  of the upper-path forming member  57 , and the right guide rail  77 R is provided in a top surface  62   a  of the lower-path forming member  62 . The guide pin  79  of the left arm  74 L is engaged with the left guide rail  77 L so as to be movable, and the guide pin  79  of the right arm  74 R is engaged with the right guide rail  77 R so as to be movable. Thus, the upper-path forming member  57  serves as a component of the U-shaped reversing path  50 , as described above, as well as a component of the reciprocation path  56 . 
     The movement of the tray  55  in the conveying direction A and the returning direction D opposite the conveying direction A is performed not only by the transportation rollers  34  but also by the auxiliary transportation mechanism  67 . The auxiliary transportation mechanism  67  moves the tray  55  located at the stored position  54  to the recording start position  60  and returns the tray  55  located at the recording start position  60  to the stored position  54 . Examples of the auxiliary transportation mechanism  67  include a rack and pinion mechanism. In this embodiment, as shown in  FIG. 13 , the auxiliary transportation mechanism  67  includes a rack  68  provided on the top surface  55   a  of the tray  55 , near the right rear corner, and a pinion  69  engaged with the rack  68 , provided at the end of the gear train  66  for transmitting motive power of the roller driving shaft  35   a.    
     The operation of the thus-configured recording apparatus according to this embodiment will be described with respect to the following situations:
     (1) When the tray is stored (accommodated);   (2) When recording is started;   (3) When recording is terminated; and   (4) When the tray is set.
 
(1) When the Tray is Stored (Accommodated) (Refer to  FIGS. 2 ,  6 ,  7 ,  11 , and  13 )
   

     When the tray  55  is located at the stored position  54 , as shown in the drawings, the left and right arms  74 L and  74 R overlie one another in a compact form and are stored in the rear space of the lower-path forming member  62 . In this state, as shown in  FIG. 2 , recording can be performed on the soft recording material P. That is, the uppermost one of the soft recording materials P accommodated in the feeding cassette  11  is fed to the U-shaped reversing path  50  by the auto feeder  3 . 
     In the U-shaped reversing path  50 , the first intermediate feeding rollers  25  and the second intermediate feeding rollers  31  apply feeding force to the soft recording material P. The soft recording material P is guided to the transportation rollers  34  by the second guide roller  29 , the outer guide surface  50   a  and the inner guide surface  50   b  of the U-shaped reversing path  50 , and the inner guide surface  37   a  of the transportation guide  37 . The transportation rollers  34  hold and transport the soft recording material P to the recording position  51 , where the recording execution unit  4  performs recording. 
     (2) When Recording is Started (Refer to  FIGS. 3 ,  9 , and  14 ) 
     The tray  55  located at the stored position  54  is first moved to the set position  53  by the auxiliary transportation mechanism  67  and the transportation rollers  34  shown in  FIGS. 5 and 16 . That is, when the motive power of the roller driving shaft  35   a  is transmitted to the rack  68  on the top surface  55   a  of the tray  55  via the gear train  66  and the pinion  69 , the tray  55  starts to move forward. Once the front end portion  80  of the tray  55  arrives at the nip point of the transportation rollers  34 , the auxiliary transportation mechanism  67  stops transmitting the motive power. Then, the transportation rollers  34  start transmitting the motive power to bring the tray  55  to the set position  53 . 
     When the hard recording material Q is set in the setting recess  71  in the tray  55 , the transportation rollers  34  bring the tray  55  back to the recording start position  60  shown in  FIGS. 3 and 14 . Then, the tray  55  is transported in the conveying direction A by the transportation force of the transportation rollers  34 . At the same time, the carriage  40  reciprocating in the width direction B causes ink of different colors to be ejected from the recording head  42  over the entire width of the recording surface of the hard recording material Q from above. Thus, recording is started. The tray  55  is used when the recording is performed on the recording surface of the hard recording material Q. Therefore, before the recording is started, a gap PG between the recording head  42  and the platen  38  is increased upward by an auto gap adjusting device (not shown) to set the gap to the gap PG for the hard recording material Q. 
     (3) When Recording is Terminated (Refer to  FIGS. 4 ,  9 , and  15 ) 
     When the tray  55  is transported to the recording termination position, the recording on the recording surface of the hard recording material Q is terminated. At this time, the front end of the tray  55  shown in  FIGS. 4 and 15  are located at the recording termination position  61 . 
     When the tray  55  is moved from the recording start position  60  to the recording termination position  61 , the transportation rollers  34  directly hold the tray  55  therebetween to apply the transportation force to the tray  55 . The accurate, stable, and smooth transportation of the tray  55  improves the recording quality. 
     (4) When the Tray is Set (Refer to  FIGS. 5 ,  8 ,  9 , and  16 ) 
     When the hard recording material Q is to be set in the tray  55  or when the hard recording material Q after recording is to be removed from the tray  55 , the tray  55  is located at the set position  53 , where it is fully drawn frontward by the amount of movement stroke S, as shown in  FIGS. 5 ,  8 ,  9 , and  16 . The tray  55  is moved from the recording termination position  61  to the set position  53  by allowing the left and right arms  74 L and  74 R to extend in the conveying direction A and by holding the arms  74 L and  74 R between the transportation rollers  34  to apply the transportation force indirectly to the tray  55 . 
     As described above, in the area in which the tray  55  is moved between the recording termination position  61  and the set position  53 , the contact surfaces  86 L and  86 R of the arms  74 L and  74 R on the transportation driving roller  35  side are flat. In addition, as described above, the positional relationship in the top-bottom direction between the tray  55  and the arm  74 L of the left connection portion  87 L is opposite to that between the tray  55  and the arm  74 R of the right connection portion  87 R. Accordingly, the tray  55  is smoothly transported while maintaining a stable orientation in the above-mentioned area as in the case where it is held between the transportation rollers  34  and receives transportation force directly. 
     The movement of the tray  55  between the stored position  54  and the set position  53 , between the recording start position  60  and the recording termination position  61 , and between the recording termination position  61  and the set position  53  causes the guide pins  79  and  79  provided at the base ends  74   b  and  74   b  of the left and right arms  74 L and  74 R to move while being engaged with the guide rails  77 L and  77 R, respectively. Thus, the orientation of the arms  74 L and  74 R is continuously changed from the orientation in which they are folded so as to overlie each other, as shown in  FIGS. 2 ,  6 ,  7 ,  11 , and  13 , to the orientation in which they are extended, as shown in  FIGS. 5 ,  8 ,  9 , and  16 . 
     The relationship between the arms  74 L,  74 R and the guide rails  77 L,  77 R when the arms  74 L and  74 R have been moved to the set position  53  will be described. 
       FIGS. 19 to 22  are partial enlarged views of the arm  74 L and the guide rail  77 L and diagrams showing the relationship between the arm  74 L and the guide rail  77 L immediately before the tray  55  moves to the set position  53 . 
       FIG. 19  is an enlarged perspective view of the vicinity of the guide pin  79 L in the sate of  FIG. 8 , in which the base end  74   b  of the arm  74 L is viewed from diagonally above. As shown in  FIG. 19 , the tip of the guide pin  79 L is in the shape of a hook and has an upper hook portion  79 La serving as a retaining portion.  FIGS. 20 and 21  are perspective views of the upper-path forming member  57  viewed from diagonally above and below, respectively, in which a part of an end of the guide rail  77 L to be engaged with the guide pin  79 L provided on the arm  74 L is enlarged. The guide rail  77 L provided in the inner surface of the upper-path forming member  57  has, at the end, a lower hook portion  77 La serving as a retaining portion. 
       FIG. 22  shows the relationship between the arm  74 L and the guide rail  77 L immediately before the tray  55  moves to the set position  53 . When the tray  55  has moved to the set position  53 , the guide pin  79 L comes into contact with the tip of the guide rail  77 L, limiting the movement of the tray  55  toward the discharge unit side. Even if the tray  55  located at the set position  53  is further pulled toward the discharge unit side by unexpected force or is moved downward by vibration, the upper hook portion  79 La of the guide pin  79 L shown in  FIG. 22  and the lower hook portion  77 La of the guide rail  77 L engage with each other to prevent the arm  74 L from coming off the guide rail  77 L. Although this embodiment is configured to leave a gap (clearance) between the upper hook portion  79 La and the lower hook portion  77 La when the tip of the guide rail  77 L and the guide pin  79 L are in contact, the upper hook portions  79   a  may be provided so as not to leave such a gap. 
       FIGS. 23 to 26  are partial enlarged views of the arm  74 R and the guide rail  77 R and diagrams showing the relationship between the arm  74 R and the guide rail  77 R immediately before the tray  55  moves to the set position  53 . 
       FIG. 23  is an enlarged perspective view of the vicinity of the base end  74   b  and the guide pin  79 R, showing the arm  74 R in  FIG. 8  in an upside-down state. As shown in  FIG. 23 , the tip of the guide pin  79 R is in the shape of a hook and has a lower hook portion  79 Ra serving as a retaining portion. 
       FIGS. 24 and 25  are perspective views of the lower-path forming member  62  viewed from diagonally above and below, respectively, in which a part of an end of the guide rail  77 R to be engaged with the guide pin  79 R provided on the arm  74 R is enlarged. The guide rail  77 R provided in the top surface of the lower-path forming member  62  has, at the end, an upper hook portion  77 Ra serving as a retaining portion. 
       FIG. 26  shows the relationship between the arm  74 R and the guide rail  77 R immediately before the tray  55  moves to the set position  53 . When the tray  55  has moved to the set position  53 , the guide pin  79 R comes into contact with the tip of the guide rail  77 R, limiting the movement of the tray  55  toward the discharge unit side. Even if the tray  55  located at the set position  53  is further pulled toward the discharge unit side by unexpected force or is moved upward by vibration, the lower hook portion  79 Ra of the guide pin  79 R shown in  FIG. 26  and the upper hook portion  77 Ra of the guide rail  77 R engage with each other to prevent the arm  74 R from coming off the guide rail  77 R. Although this embodiment is configured to leave a gap (clearance) between the lower hook portion  79 Ra and the upper hook portion  77 Ra when the tip of the guide rail  77 R and the guide pin  79 R are in contact, the upper hook portions  79   a  may be provided so as not to leave such a gap. 
     As has been described, by preventing the guide pins  79 L and  79 R of the arms  74 L and  74 R from coming off the guide rails  77 L and  77 R with the hook-shaped retaining portions when the tray  55  has moved to the set position  53 , the tray  55  is also prevented from coming off the printer main body  2 . 
     In the above-described retaining structure, the upper hook portion  79 La and the lower hook portion  79 Ra are provided at the tips of the guide pins  79 L and  79 R of the arms  74 L and  74 R, respectively, and the lower hook portion  77 La and the upper hook portion  77 Ra are provided at the tips of the guide rails  77 L and  77 R, respectively, so that the arms  74 L and  74 R and the guide rails  77 L and  77 R are engaged. However, as long as the arms  74 L and  74 R can be prevented from coming off the guide rails  77 L and  77 R, the retaining structure is not limited to that having a hook structure as described above. 
     The operation of the recording-medium transportation unit  5  when the tray  55  returns from the set position  53  to the stored position  54  is the same as that when the tray  55  moves from the stored position  54  to the set position  53  except that the operation proceeds in reverse order. 
     Second Embodiment 
     Although the structure of the ink jet printer  1  having the recording-medium transportation unit  5  of the invention, serving as a recording apparatus, is basically as described above, the structure may of course be partially modified or omitted within the scope of the invention. 
     For example, as shown in  FIG. 17 , the arms  74  do not have to be connected to the tray  55  at the left and right rear corners of the tray  55 , but may be at the central portion of the rear end of the tray  55 .  FIG. 17  shows an extendable moving mechanism  59 A that moves like a pantograph and has the left and right arms  74 L and  74 R each consisting of two arm elements, namely, arm elements  89 A and  90 A and arm elements  89 B and  90 B. The left and right arms  74 L and  74 R are each bent at fulcrums  88 L and  88 R. 
     Third Embodiment 
     The extendable moving mechanism  59  is not limited to one having the above-described arms  74 . For example, as shown in  FIG. 18 , the extendable moving mechanism  59  may be an extendable moving mechanism  59 B in which a plurality of linkage pieces  91  are connected so as to be pivotable in a chain form or a shutter form. In  FIG. 18 , the extendable moving mechanism  59 B is configured such that the linkage pieces  91  are rolled upward in the space between the tray  55  and the upper-path forming member  57 . 
     The width of the linkage pieces  91  may be either small or large. In the case of the linkage pieces  91  with a small width, a plurality of sets of the linkage pieces  91  may be provided (for example, two sets of the linkage pieces  91  may be provided at the left and right rear corners of the tray  55 ). On the other hand, if the width of the linkage pieces  91  is increased to the maximum extent, that is, to the same width as the tray  55 , a shutter-like extendable moving mechanism  59 B is obtained. The linkage pieces  91  do not necessarily have to be rolled upward, but may be rolled downward, leftward, or rightward. 
     Other Embodiments 
     Furthermore, for example, the transportation path for the soft recording material P is not limited to the above-described U-shaped reversing path  50 , but may be a straight transportation path that transports the soft recording material P from the feeding tray provided at a rear upper portion of the printer main body  2  toward the discharging stacker  47  projecting from the front surface  2   a  of the printer main body  2 . 
     Furthermore, a recording-medium transportation unit or an ink jet printer dedicated for hard recording materials, which has no transportation path for soft recording materials, is also possible. In addition, the recording-medium transportation unit  5  of the invention may be applied to devices other than the ink jet printer  1 , for example, DVD players or personal computers. 
     Furthermore, the structure of the extendable moving mechanism  59  may be, in addition to one employing two arms  74 L and  74 R and two guide rails  77 L and  77 R as described above, one employing three or more arms  74  and three or more guide rails  77  or one employing only one arm  74  and one guide rail  77 .