Patent Publication Number: US-2005127725-A1

Title: Seat unit

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a seat unit with a tray table provided on one side of a seat cushion for holding various kinds of articles.  
      2. Description of the Related Art  
      A prior art example of a seat unit of this kind is found in Japanese Unexamined Patent Publication No. 1995-315097, for instance, in which a tray table  101  is provided on one side of a seat cushion  100 , on which a vehicle occupant is seated, for holding various articles, and the tray table  101  can be flipped down from a horizontal position shown in  FIG. 25A  to a vertically hanging storage position shown in  FIG. 25B , and vice versa, as necessary.  
      The aforementioned conventional tray table  101  is disposed on the side of the seat cushion  100  and can be folded down to the storage position to reduce overall width when not in use. This structure of the tray table  101  offers a certain degree of so-called walk-through capability by providing an extra space beside the seat cushion  100  to allow a passenger in a rear seat to move forward. Even when the tray table  101  has been shifted to the storage position, however, the vertically hanging tray table  101  remains on the side of the seat cushion  100 , so that the tray table  101  id the storage position inevitably interferes with a moving passenger limiting internal walk-through access. From this point of view, there has been a room for improving the tray table structure.  
     SUMMARY OF THE INVENTION  
      In light of the foregoing, it is an object of the invention to provide a seat unit equipped with a tray table which can be used for holding articles when necessary and can be stored when unnecessary so that the tray table would not interfere with internal walk-through access of a vehicle.  
      According to the present invention, a seat unit includes a seat cushion, a tray compartment located under the seat cushion, a tray which is made storable in the tray compartment, a seat cushion swing mechanism which makes it possible to expose the top side of the tray compartment by swinging up the seat cushion about a support shaft provided at one end of the seat cushion, and a tray support provided on a seat-side member for supporting the tray in such a manner that the tray can be moved between a storage position inside the tray compartment and a service position on one side of the seat cushion after swinging up the seat cushion.  
      In this structure, the tray supported by the tray support can be folded out to the service position located on one side of the seat cushion with the top side of the tray compartment exposed by swinging up the seat cushion about the support shaft provided at one end of the seat cushion so that the tray can be used as a platform for holding various articles when necessary. When it is not necessary to use the tray, the tray can be stowed back to the storage position located under the seat cushion so that a free space is created on one side of the seat cushion to provide an improved walk-through capability for passengers.  
      These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description along with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a plan view generally showing the structure of a motor vehicle equipped with a seat unit according to a preferred embodiment of the invention;  
       FIG. 2  is a perspective view of the seat unit according to the embodiment of the invention;  
       FIG. 3  is a cross-sectional front view of a principal part of the seat unit of  FIG. 2 ;  
       FIG. 4  is a plan view showing a specific structure of a tray;  
       FIG. 5  is a perspective view showing the specific structure of the tray;  
       FIG. 6  is a cross-sectional front view showing the specific structure of the tray;  
       FIG. 7  is a cross-sectional side view of the tray of  FIG. 4  set in a service position and a storage position;  
       FIGS. 8A, 8B  and  8 C are cross-sectional side views specifically showing the structure of a tray main part;  
       FIG. 9  is a perspective view showing how a flexible container is attached to the tray;  
       FIG. 10  is a perspective view showing how more than one flexible containers are attached to the tray,  
       FIG. 11  is a plan view of a tray according to another form of embodiment of the invention;  
       FIG. 12  is a cross-sectional side view of the tray of  FIG. 11  set in a service position and a storage position;  
       FIG. 13  is a cross-sectional side view specifically showing the structure of a retainer for holding a cover plate of the tray of  FIG. 11 ;  
       FIG. 14  is a perspective view showing a varied form of the tray;  
       FIG. 15  is a side view particularly showing the structure of a supporting tab of a cover plate in the varied form of the tray of  FIG. 14 ;  
       FIG. 16  is a partially cross-sectional plan view showing the structure of the supporting tab of the cover plate and a tab fitting part formed in a tray main part of the tray of  FIG. 14 ;  
       FIG. 17  is a cross-sectional side view showing a closed position of the cover plate of the tray of  FIG. 14 ;  
       FIG. 18  is a cross-sectional side view showing an open position of the cover plate of the tray of  FIG. 14 ;  
       FIG. 19  is a cross-sectional side view particularly showing the structure of a retainer for holding the cover plate in one variation of the embodiment;  
       FIG. 20  is a cross-sectional side view particularly showing the structure of fixing parts for fixing the tray main part in one variation of the embodiment;  
       FIG. 21  is a plan view showing a state in which the tray is set in its service position;  
       FIG. 22  is a side view showing a state in which the tray is set in its service position;  
       FIG. 23  is a side view showing a state in which an in-vehicle facility is set in its service position;  
       FIG. 24  is a cross-sectional front view showing the state in which the in-vehicle facility is set in its service position; and  
       FIGS. 25A and 25B  are perspective views showing a conventional seat unit equipped with a flip-up tray table.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION  
       FIG. 1  is a plan view generally showing the structure of a motor vehicle  30  equipped with first-row seats  31  at the front of a passenger compartment, second-row seats  32  located just behind the first-row seats  31 , and a third-row seat  33  located just behind the second-row seats  32 . While the first-row seats  31  and the second-row seats  32  are pairs of bucket seats separately installed on left and right sides of the first and second rows, respectively, the third-row seat  33  is a single bench-style seat. Among these seats, the second-row bucket seat  32  installed on the right side of the second row is a seat unit  1  according to a preferred embodiment of the invention.  
      The seat unit  1  of the present embodiment includes a pair of left and right guide rails  2  firmly fixed to a floor of a vehicle body, a pair of left and right slide members  4  supported slidably along the guide rails  2 , a seat cushion  3  mounted on the slide members  4  and a backrest  5  supported tiltably about a horizontal shaft (not shown) provided at rear ends of the slide members  4 .  
      Provided at front ends of the slide members  4  is a horizontally elongate support shaft  6  of a seat cushion swing mechanism  20  by which the seat cushion  3  is swingably supported. More specifically, a cushion frame (not shown) disposed below the seat cushion  3 , for instance, is supported by the slide members  4  via the support shaft  6 , and as the seat cushion  3  is swung, or lifted, up and down about the support shaft  6 , the seat cushion  3  moves between an upright position at which a rear end of the seat cushion  3  is raised as illustrated by imaginary lines in  FIG. 2  and a normal seating position at which the seat cushion  3  lies generally horizontally on the slide members  4 .  
      The seat unit  1  is equipped with a tray  10  for holding articles and a tray support  21  for supporting the tray  10 . The tray support  21  includes a pair of front and rear brackets  23  attached to an inner side surface of the left-hand slide member  4  which is a seat-equipped mechanical member and a horizontal shaft  24  fitted between upper parts of the two brackets  23 , and a later-described supporting frame  12  of the tray  10  is supported by the brackets  23  via the horizontal shaft  24 . The tray support  21  is structured such that the tray  10  can be moved between a service position a at which the tray  10  sticks out sideways and a storage position β at which the tray  10  is stored in a tray compartment  7  located beneath the seat cushion  3  by swinging the tray  10  about the horizontal shaft  24  with the seat cushion  3  raised to the upright position as illustrated in  FIG. 2 .  
      The tray  10  includes a tray main part  11  having a generally rectangular shape in top view made of synthetic resin, for example, and the aforementioned supporting frame  12  attached to the bottom of the tray main part  11 . The tray main part  11  has a generally rectangular outer framing portion  14  in which a downward opening groove is made on the bottom side, four hooks  13  extending upward from lower ends of four corners of the outer framing portion  14  and reinforcing ribs  14   c  formed in the groove in the outer framing portion  14  at specific intervals as shown in FIGS.  4  to  6 .  
      Formed on the inside of the outer framing portion  14  of the tray main part  11  is a recess  15  located on a front side serving as holders for beverage receptacles and a flat portion  16  located on a rear side for holding various articles. The tray main part  11  is shaped such that the flat portion  16  is located at a height lower than a top surface of the outer framing portion  14 , forming a flat surface like that of a dish for holding articles. As can be seen from  FIG. 6 , there is formed a generally rectangular through hole  16 a of which size is a little smaller than the flat portion  16  in the tray main part  11 , and the flat portion  16  is made by fitting a generally rectangular flat cover plate  17  to cover the through hole  16   a.  The recess  15  has a pair of left and right cylindrical holes in which lower parts of beverage receptacles are fitted and a joining channel interconnecting the left and right holes.  
      The supporting frame  12  has a main portion  12   a  which is generally C-shaped in top view and a pair of front and rear arms  12   b  extending from both ends of the main portion  12   a  as shown in  FIG. 5 . The tray main part  11  is structured such that the main portion  12   a  of the supporting frame  12  can be fitted into the outer framing portion  14  of the tray main part  11  from the bottom side thereof. Each of the arms  12   b  of the supporting frame  12  has a vertical portion extending downward from one end of the main portion  12   a  and a horizontally projecting portion extending outward from a bottom end of the vertical portion, and there are formed shaft holes  12   c  in which the aforementioned horizontal shaft  24  is fitted near extreme ends of the horizontally projecting portions of the arms  12   b.    
      In an inside part of a right-hand hollow straight section of the main portion  12   a  of the supporting frame  12  as viewed from the front of the vehicle body ( FIG. 6 ), there are formed a plurality of mating holes  12   d  into which hookup protrusions  14   a  formed on the outer framing portion  14  of the tray main part  11  are fitted. In an outside part of a left-hand hollow straight section of the main portion  12   a  of the supporting frame  12  as viewed from the front of the vehicle body ( FIG. 6 ), on the other hand, there are also formed a plurality of mating holes  12   d  into which fixing bolts  18  are tightened from outside a plurality of through holes formed in the outer framing portion  14  of the tray main part  11 . When the main portion  12   a  of the supporting frame  12  is fitted into the outer framing portion  14  of the tray main part  11  from the bottom side thereof as stated above up to a point where an upper part of the main portion  12   a  of the supporting frame  12  comes into contact with bottom ends of the reinforcing ribs  14   c,  the hookup protrusions  14   a  formed on the outer framing portion  14  of the tray main part  11  fit into the mating holes  12   d  formed in the right-hand hollow straight section of the main portion  12   a  of the supporting frame  12 . The fixing bolts  18  are tightened into the mating holes  12   d  formed in the left-hand hollow straight section of the main portion  12   a  of the supporting frame  12  as illustrated in  FIG. 6 , whereby the tray main part  11  is secured to the supporting frame  12 . In this structure of the embodiment, the hookup protrusions  14   a  and the fixing bolts  18  together constitute fixing parts.  
      As illustrated in  FIGS. 5 and 6 , the supporting frame  12  is fitted with brackets  19  made of shaped wires for supporting the tray main part  11  with part of the bottom of the tray main part  11  located inside the supporting frame  12  lying on the wire frames  19 . Each of these wire frames  19  has a pair of fixing parts located at both ends which are attached to the bottom of the main portion  12   a  of the supporting frame  12  and a generally horizontal central arm projecting inward from the main portion  12   a.  The tray main part  11  is supported by the wire frames  19  with the bottom of the tray main part  11  held in contact with the projecting arms of the wire frames  19 .  
      A net bag  25  having an upper opening serving as a utility storage container is provided underneath the tray  10 . Upper edges of the net bag  25  along an opening  25   a  at the upper end of the net bag  25  are placed in the outer framing portion  14  of the tray main part  11  and clamped between the outer framing portion  14  and the supporting frame  12 . The net bag  25  fitted to the tray  10  in this way hangs from the tray  10  as shown in  FIG. 3 . More specifically, the hookup protrusions  14   a  and the fixing bolts  18  together constituting the fixing parts are passed through meshes of the net bag  25  or hooking slits formed therein, whereby the upper opening  25   a  of the net bag  25  is fixed to the outer framing portion  14  of the tray main part  11 .  
      The height H 1  of the net bag  25  constituting the utility storage container from the upper opening  25   a  to the bottom of the net bag  25  is made smaller than the height H 2  of the tray compartment  7  from an upper end thereof to the opening  25   a  of the net bag  25  as measured when the tray  10  is retracted to its storage position βas shown in  FIG. 3 . A seat-side member  4   a  is fitted to the outside of the left-hand (right-hand as illustrated in  FIG. 3 ) slide member  4  of the right-hand second-row seat  32 , and a cushion pad  22  made of synthetic rubber, for example, is attached to a top surface of the seat-side member  4   a.  When the tray  10  is folded out to its service position α, the arms  12   b  of the supporting frame  12  rest on the cushion pad  22  of the seat-side member  4   a  in direct contact therewith.  
      At the middle of a rear side of the through hole  16   a  formed at the flat portion  16  of the tray main part  11 , there is formed a slit  16   b  in the outer framing portion  14 , and a ridge  17   a  formed on a rear end of the cover plate  17  is fitted into this slit  16   b  (refer to  FIG. 8A ). Also, on a front side of the through hole  16   a  at the flat portion  16  of the tray main part  11 , there are formed stepped ridges  16   c  projecting rearward from portions of the front side of the through hole  16   a,  and not from a middle portion thereof, and locking parts  17   b  formed on a front end of the cover plate  17  fit onto the stepped ridges  16   c  on the front side of the through hole  16   a  at the flat portion  16  of the tray main part  11  (refer to  FIG. 8B ). When the ridge  17   a  formed on the cover plate  17  is inserted into the slit  16   b  formed at the flat portion  16  of the tray main part  11  and the locking parts  17   b  of the cover plate  17  are mated with the stepped ridges  16   c  on the front side of the through hole  16   a  at the flat portion  16  of the tray main part  11 , the cover plate  17  is locked in position closing the through hole  16   a.    
      As shown in  FIG. 8C , there is formed a projection  16   d  at the bottom of the outer framing portion  14  of the tray main part  11  extending rearward from the middle of the front side of the through hole  16   a  with a cutout formed just above the projection  16   d  for creating a clearance S 2  between the outer framing portion  14  and the front end of the cover plate  17 . Further, there is formed a hang-on part  17   c  extending flush with a top surface of the cover plate  17  from the middle of the front end thereof, the hang-on part  17   c  facing the projection  16   d  of the outer framing portion  14  with a clearance S 1  in between. This arrangement makes it possible to easily lift the front end of the cover plate  17  with a fingertip inserted into a space created by the clearances S 1  and S 2  and remove the cover plate  17  upon releasing the locking parts  17   b  of the cover plate  17  from the stepped ridges  16   c  at the front side of the through hole  16   a  in the flat portion  16  of the tray main part  11 .  
      As illustrated in the foregoing discussion, the structure of the embodiment includes the seat cushion  3 , the tray compartment  7  provided underneath the seat cushion  3 , the tray  10  storable in the tray compartment  7  and the seat cushion swing mechanism  20  which makes it possible to expose the top side of the tray compartment  7  by swinging up the seat cushion  3  about the support shaft  6  at one end of the seat cushion  3 . The tray support  21  sustains the tray  10  in such a manner that the tray  10  can be moved between the service position α and the storage position β in the tray compartment  7  located under the seat cushion  3  under conditions where the top side of the tray compartment  7  is exposed with the seat cushion  3  swung up as shown by the imaginary lines in  FIG. 2 . Since this tray support  21  is attached to the seat-equipped mechanical member, or the left-hand slide member  4  of the seat unit  1  of  FIG. 2 , the tray  10  can be pulled out to the service position α on the left side of the seat cushion  3  whenever it is desired to place articles on the tray  10 . When it is not necessary to use the tray  10 , the tray  10  can be stowed back to the storage position β in the tray compartment  7  so that a free space is created on the left side of the seat cushion  3 , thereby providing an improved walk-through capability for passengers.  
      The structure of the aforementioned embodiment is provided with the utility storage container made of the net bag  25  which has an upper opening and hangs from the tray  10  when the tray  10  is set in the storage position β, the through hole  16   a  joining the upper opening of the net bag  25  to a space above the tray  10 , and the cover plate  17  which covers or uncovers the through hole  16   a.  This arrangement of the embodiment makes it possible to place and take out articles in and from the net bag  25  through the through hole  16   a  upon lifting up the cover plate  17  when the tray  10  is in the service position α. This arrangement is also advantageous in that the cover plate  17  can be used as a platform for holding various articles when set in position to cover the through hole  16   a.    
      According to the foregoing embodiment, the recess  15  for holding beverage receptacles and the flat portion  16  for holding articles are located in separate areas and the flat portion  16  of the tray main part  11  is formed by the removable cover plate  17 . This structure enables a passenger to place and take out articles in and from the net bag  25  upon lifting up the cover plate  17  without accidentally touching the beverage receptacles held in the recess  15  and spilling their contents. The structure of the embodiment also enables the passenger to easily place and remove the beverage receptacles in and from the recess  15  regardless of whether the cover plate  17  is set in position or not.  
      According to the foregoing embodiment, the tray  10  includes the tray main part  11  having the recess  15  for holding beverage receptacles and the flat portion  16  for holding articles as well as the supporting frame  12  to which the tray main part  11  is fixed by means of the fixing parts including the hookup protrusions  14   a  and the fixing bolts  18 , and the net bag  25  constituting the utility storage container is attached to the tray  10  by the aforementioned fixing parts. This structure of the embodiment is advantageous in that the net bag  25  constituting the utility storage container can be compactly stored in the tray compartment  7  with ease when it is not necessary to use the tray  10 . The structure of the embodiment is also advantageous in that the tray main part  11  can be attached to the supporting frame  12  without the need for any dedicated fixtures and the utility storage container made of the net bag  25  can be attached to the tray  10  with a simple arrangement.  
      Furthermore, the supporting frame  12  is fitted with the wire frames  19  for supporting the tray main part  11  located inside the supporting frame  12  in the foregoing embodiment. This arrangement is advantageous in that the stiffness of the supporting frame  12  can be effectively increased by a simple structure so that the supporting frame  12  can support the tray main part  11  in a stable manner.  
      Moreover, the utility storage container is made of a pouchlike flexible container similar to the net bag  25  and the height H 1  of the net bag  25  from the upper opening  25   a  to the bottom of the net bag  25  is made smaller than the height H 2  of the tray compartment  7  from the upper end thereof to the opening  25   a  of the utility storage container (net bag  25 ) as measured when the tray  10  is retracted to its storage position β in the foregoing embodiment. This arrangement ensures that the bottom of the utility storage container would not project from the tray compartment  7  beyond the upper end thereof when the tray  10  is stowed in the tray compartment  7  with the utility storage container attached to the tray  10 . Therefore, the arrangement serves to effectively prevent the bottom of the utility storage container from being caught between the top of the tray compartment  7  and the bottom of the seat cushion  3 .  
      According to the invention, the present embodiment may be modified such that the seat unit  1  employs, instead of the aforementioned arrangement in which the utility storage container made of the net bag  25  is attached to the tray  10  by means of the fixing parts including the hookup protrusions  14   a  and the fixing bolts  18 , an arrangement in which an utility storage container made of a pouchlike flexible container is attached to the tray  10  by means of the hooks  13  formed on an outer periphery of the tray main part  11 . For example, a flexible container  26 , such as a plastic shopping bag, may be suspended from the tray main part  11  to cover the bottom side of the tray  10  with hooking parts  26   a  of the flexible container  26  (handles of the shopping bag) provided at an upper end thereof hooked on the hooks  13  located at the four corners of the tray main part  11  as shown in  FIG. 9 . This alternative arrangement is advantageous in that a widely available shopping bag suspended from the tray  10  can be used as a waste disposal bag which can be easily removed whenever desired.  
      The present embodiment may also be modified such that the seat unit  1  employs, instead of the aforementioned arrangement in which the single flexible container  26  is attached to the tray main part  11  to cover the bottom side of the tray  10 , an arrangement in which two or more flexible containers  26 , such as plastic shopping bags, are suspended from the front and rear of the tray  10  as shown in  FIG. 10 , for instance. As previously mentioned, the tray  10  has the through hole  16   a  joining the top and bottom sides of the tray  10  and the cover plate  17  which covers or uncovers the through hole  16   a  and the hooks  13  are formed on the outer periphery of the tray main part  11 . This arrangement is advantageous in that widely available shopping bags or the like cap be suspended from desired positions by attaching hooking parts (handles)  26   a  of the flexible containers  26  to the hooks  13  when necessary and easily removed.  
      While the through hole  16   a  joining the top and bottom sides of the tray  10  is formed in an almost entire area of the flat portion  16  of the tray main part  11  in the foregoing embodiment, the location and the size of the through hole  16   a  are not limited to this structure of the embodiment but may be modified in various ways. As an example, the seat unit  1  may employ a structure in which a trough hole joining the top and bottom sides of the tray  10  is formed in part of the entire area of the flat portion  16  and a cover plate for covering and uncovering the trough hole is placed on the tray  10 .  
       FIGS. 11, 12  and  13  are diagrams showing a seat unit  1  according to another form of embodiment of the invention. The seat unit  1  of this embodiment is equipped with a tray  40  of which cover plate  43  provided at a flat portion  42  of a tray main part  41  can be opened and closed by means of a pair of hinges  44 . Specifically, a through hole  42   a  joining the top and bottom sides of the tray  40  except for a front part  42   b  of the flat portion  42  is formed in the flat portion  42  of the tray main part  41 , and the cover plate  43  for covering and uncovering the through hole  42   a  is supported swingably about the hinges  44  located at a front end of the cover plate  43 .  
      The cover plate  43  has at its rear end a finger-operated tab  43   a  which lies on a rearmost end of an outer framing portion  41   a  of the-tray main part  41  as well as a retainer  45  which is located between the finger-operated tab  43   a  and the outer framing portion  41   a  of the tray main part  41 . The retainer  45  includes a permanent magnet  45   a  affixed to a top surface of the outer framing portion  41   a  of the tray main part  41  and a piece of ferromagnetic substance  45   b,  such as a flat steel bar, affixed to a bottom surface of the finger-operated tab  43   a  so that the cover plate  43  is normally held in its closed position by a magnetic force exerted by the permanent magnet  45   a.    
      According to the aforementioned structure of this embodiment, the cover plate  43  can be moved to its upper open position by lifting the finger-operated tab  43   a  of the cover plate  43  from its closed position to release the ferromagnetic piece  45   b  from the permanent magnet  45   a  and swinging up the cover plate  43  about the hinges  44 . The structure of this embodiment is advantageous in that when the tray  40  is set to its storage position β with the through hole  42   a  closed by the cover plate  43 , the cover plate  43  is held in its closed position by the magnetic force exerted by the permanent magnet  45   a.    
      According to the invention, the present embodiment may be modified such that the “seat” unit  1  employs, instead of the aforementioned arrangement in which the cover plate  43  is swingably supported by the hinges  44 , an arrangement shown in  FIG. 14  in which the cover plate  43  for covering and uncovering the through hole  42   a  in the tray main part  41  has a finger-operated part  46  formed at a free end (front end) of the cover plate  43  that is used when opening the cover plate  43  and a supporting tab  47  formed at a fixed end (rear end) of the cover plate  43  that serves as a pivot shaft about which the cover plate  43  is swung up and down, and a tab fitting part  48  is formed in the tray main part  41  such that the supporting tab  47  of the cover plate  43  can be detachably fitted to the tab fitting part  48  of the tray main part  41 .  
      Shaped as illustrated in  FIGS. 15 and 16 , the supporting tab  47  of the cover plate  43  according to the aforementioned varied form of the embodiment has a vertical portion  47   a  extending downward from the fixed end of the cover plate  43 , a horizontal portion  47   b  extending horizontally frontward from a lower end of the vertical portion  47   a  and a pair of hemispherical protrusions  47   c  formed on both left and right end surfaces of the horizontal portion  47   b.  On the other hand, the tab fitting part  48  formed in the tray main part  41  has a tab fitting opening  48   a  having a width corresponding to the width of the vertical portion  47   a  and the horizontal portion  47   b  of the supporting tab  47 , a pair of left and right cut portions  48   b  formed at a rear end of the tab fitting opening  48   a  and a pair of left and right protruding stopper portions  48   c  jutting out inward from a front end of the tab fitting opening  48   a.  The distance W 1  between the left and right cut portions  48   b  is made a little larger than the distance WO between the left and right protrusions  47   c,  and the distance W 2  between the left and right protruding stopper portions  48   c  is made a little smaller than the distance WO between the two protrusions  47   c.    
      The cover plate  43  structured as explained above is fitted to the tray main part  41  as follows. After passing the protrusions  47   c  formed on the left and right end surfaces of the supporting tab  47  of the cover plate  43  downward between the cut portions  48   b  of the tab fitting part  48  of the tray main part  41  from above, the cover plate  43  is placed on the tray main part  41  as shown in  FIG. 17  so that the cover plate  43  closes the through hole  42   a  in the tray main part  41 . Then, the cover plate  43  is moved to its open position as shown in  FIG. 18  by lifting and swinging the free end of the cover plate  43  with a fingertip hooked on the finger-operated part  46 . When the cover plate  43  is turned to the open position, the protrusions  47   c  on the left And right end surfaces of the horizontal portion  47   b  of the supporting tab  47  go into contact with the left and right protruding stopper portions  48   c  formed at the tab fitting part  48 , whereby the cover plate  43  is held at the open position.  
      The cover plate  43  can be removed from the tray main part  41  by lifting the cover plate  43  so that the protrusions  47   c  formed on the left and right end surfaces of the supporting tab  47  of the cover plate  43  pass through the tab fitting part  48  upward from below the tray main part  41  to a space above the through hole  42   a  reversing the aforementioned procedure used when fitting the cover plate  43 . The aforementioned structure in which the supporting tab  47  of the cover plate  43  is detachably fitted into the tab fitting part  48  of the tray main part  41  is advantageous in that an entire area of the through hole  42   a  can be held open by removing the cover plate  43  from the tray main part  41  and storing the cover plate  43  in a specified location when the cover plate  43  is not necessary. The cover plate  43  can also be removed from the tray main part  41  by further turning the cover plate  43  in its opening direction from the open position shown in  FIG. 18 , causing the protruding stopper portions  48   c  of the tab fitting part  48  to elastically deform and the protrusions  47   c  of the supporting tab  47  to be released from the protruding stopper portions  48   c,  instead of lifting the cover plate  43  upward as discussed above.  
      The present embodiment may also be modified such that the seat unit  1  employs, instead of the aforementioned arrangement ( FIG. 13 ) in which the cover plate  43  is held in the closed position by the magnetic force exerted by the permanent magnet  45   a,  an arrangement in which the cover plate  43  is fitted with a snap-in clip  49  located near the free end of the cover plate  43  and detachably locked in the closed position by forcing the snap-in clip  49  into a retaining hole  50  formed in the tray main part  41  as shown in  FIG. 19 .  
      Also, the foregoing embodiment may be modified such that the seat unit  1  employs, instead of the aforementioned arrangement ( FIG. 6 ) in which the tray main part  11  is fixed to the supporting frame  12  and the net bag  25  is attached to the tray  10  by the fixing parts including the hookup protrusions  14   a  and the fixing bolts  18 , an arrangement in which snap-in clips  51  are fitted in the outer framing portion  14  of tray main part  11  and upward projecting retaining brackets  53  individually having retaining holes  52  are affixed to upper parts of the supporting frame  12  as shown in  FIG. 20 , whereby the tray main part  11  is fixed to the supporting frame  12  and the net bag  25  is attached to the tray  10  by fixing parts including the snap-in clips  51  and the retaining brackets  53  with the net bag  25  hanging from the tray  10 . More specifically, with the retaining brackets  53  passed through meshes of the net bag  25  or hooking slits formed therein, the snap-in clips  51  are forced into the retaining holes  52  formed in the individual retaining brackets  53  so that the tray main part  11  is fixed to the supporting frame  12  and the net bag  25  is attached to the tray  10  at the same time.  
      Furthermore, the seat unit  1  of the foregoing embodiment may be structured such that the cushion pad  22  attached to the top surface of the seat-side member  4   a  for the supporting frame  12  shown in  FIGS. 3, 21  and  22  is used also as a support for an in-vehicle facility  54 , such as an auxiliary seat or a side table disposed between the left and right second-row seats  32  as shown in  FIGS. 23 and 24 . More particularly, the cushion pad  22  of this variation covers an area where the arms  12   b  of the supporting frame  12  lie when the tray  10  is set in the service position α as shown in  FIG. 22  as well as an area where a leg  55  of the in-vehicle facility  54  lies when the in-vehicle facility  54  is set in its service position, so that the cushion pad  22  serves as a resilient support for both the tray  10  and the in-vehicle facility  54 . This arrangement is advantageous in that the tray  10  or the in-vehicle facility  54 , whichever used, can be supported in a stable fashion with a sufficient cushioning effect with a simple structure.  
      While the foregoing discussion has illustrated the preferred embodiment of the invention and the variations thereof, by way of example, with reference to the seat unit  1  of which right-hand second-row seat  32  is equipped with the tray  10  of the invention, the invention is not limited to this structure. For example, a tray of the invention may be provided at the left-hand second-row seat  32 , the left-hand first-row seat  31  or the right-hand first-row seat  31 . Also, the bench-style third-row seat  33  may replaced by left and right bucket seats with a tray of the invention provided at the left-hand or right-hand third-row seat.  
      While the foregoing discussion has illustrated an example of implementation of the invention in which the seat cushion  3  is swung up about the support shaft  6  located at the front of the seat cushion  3 , the seat unit  1  may be modified such that the seat cushion  3  can be swung up about a support shaft provided at the rear of the seat cushion  3  or on the side of the seat cushion  3  opposite to the side of the service position α of the tray  10  ( 40 ) to expose the top side of the tray compartment  7 . Also, the seat cushion swing mechanism  20  may be provided with a biasing member for forcing the seat cushion  3  upward so that the seat cushion  3  once released from its normal position for exposing the top side of the tray compartment  7  automatically swings up with the aid of an upward biasing force exerted by the biasing member.  
      Furthermore, the foregoing embodiment may be modified such that the seat unit  1  employs, instead of the aforementioned arrangement in which the seat cushion  3  is made swingable about the support shaft  6  or an equivalent thereof for exposing the top side of the tray compartment  7 , an arrangement in which the top side of the tray compartment  7  is exposed by removing the seat cushion  3  from the guide rails  2 .  
      In the foregoing embodiment, the seat unit  1  having the seat cushion  3 , the tray compartment  7  located beneath the seat cushion  3  and the tray  10  storable in the tray compartment  7  is structured such that the seat cushion  3  can be moved between a first position at which the top side of the tray compartment  7  is exposed and a second position at which the top side of the tray compartment  7  is closed and the tray  10  can be moved between the service position β at which the tray  10  is stored in the tray compartment  7  and the service position α at which the tray  10  is located on one side of the seat cushion  3 . This structure is advantageous in that it is possible to efficiently provide an improved walk-through capability on the side of the seat cushion  3  by storing the tray  10  in the tray compartment  7  when the tray  10  is not necessary.  
      In summary, a seat unit according to the present invention includes a seat cushion, a tray compartment located under the seat cushion, a tray which is made storable in the tray compartment, a seat cushion swing mechanism which makes it possible to expose the top side of the tray compartment by swinging up the seat cushion about a support shaft provided at one end of the seat cushion, and a tray support provided on a seat-side member for supporting the tray in such a manner that the tray can be moved between a storage position inside the tray compartment and a service position on one side of the seat cushion after swinging up the seat cushion.  
      In this structure, the tray supported by the tray support can be folded out to the service position located on one side of the seat cushion with the top side of the tray compartment exposed by swinging up the seat cushion about the support shaft provided at one end of the seat cushion so that the tray can be used as a platform for holding various articles when necessary. When it is not necessary to use the tray, the tray can be stowed back to the storage position located under the seat cushion so that a free space is created on one side of the seat cushion to provide an improved walk-through capability for passengers.  
      In one feature of the invention, a storage container having an upper opening is attached to the tray in such a manner that the storage container hangs from the tray when the tray is set at the service position, and the tray has a through hole joining the upper opening of the storage container to a space above the tray and a cover plate by which the through hole can be covered and uncovered.  
      The seat unit thus structured is advantageous in that, with the tray set in the service position, passengers can place and take out articles in and from the storage container through the through hole in the tray when the cover plate is opened and use the cover plate as a platform for holding various articles when the through hole is closed by the cover plate.  
      In anther feature of the invention, the tray has a recess for holding one or more beverage receptacles and a flat portion for holding miscellaneous articles, the cover plate being disposed at the flat portion of the tray.  
      According to this feature of the invention, the aforementioned recess for holding beverage receptacles and the flat portion for holding miscellaneous articles are provided in separate areas of the tray. This structure is advantageous in that a passenger can place and take out articles in and from the storage container upon lifting up the cover plate at the flat portion of the tray without accidentally touching the beverage receptacles and spilling their contents.  
      In anther feature of the invention, the tray includes a tray main part having the aforementioned recess and flat portion and a supporting frame to which the tray main part is fixed by fixing parts, and the storage container is made of a net bag which is attached to the tray by means of the fixing parts.  
      According to this structure, the aforementioned storage container made of a net bag can be compactly stored with ease when the tray is not necessary. In addition, the net bag can be easily attached to the tray by using the fixing parts for fixing the tray main part to the supporting frame, without the need for any dedicated fixing device.  
      In anther feature of the invention, the aforementioned supporting frame of the tray has wire frames for supporting the tray main part located inside the supporting frame with the bottom of the tray main part lying on the wire frames.  
      With this arrangement, the tray main part located inside the supporting frame can be supported by the aforementioned wire frames having a simple structure. Additionally, the provision of the wire frames effectively increases the stiffness of the supporting frame.  
      In anther feature of the invention, the aforementioned storage container is made of a flexible container having a plurality of hooking parts, and the tray has hooks on which the hooking parts of the flexible container are hooked.  
      This arrangement is advantageous in that the storage container made of a flexible container can be suspended from the tray with the hooking parts of the flexible container hooked on the hooks of the tray so that the flexible container can be used for storing goods and easily removed from the tray when desired.  
      In anther feature of the invention, the aforementioned tray has a through hole joining the top and bottom sides of the tray and a cover plate by which the through hole can be covered and uncovered, and a plurality of hooks are provided on an outer periphery of the tray.  
      According to this feature of the invention, a flexible container like a plastic shopping bag can be used for storing goods by hooking handles of the flexible container on the aforementioned hooks when the tray is set to the service position.  
      In still anther feature of the invention, the aforementioned cover plate has a finger-operated part at one end and a supporting tab at the opposite end so that the cover plate can be swung up and down about the supporting tab, and the tray is provided with a tab fitting part to which the aforementioned supporting tab of the cover plate can be detachably fitted.  
      According to this feature of the invention, it is possible to open the through hole in the tray by swinging up the cover plate by lifting the finger-operated part thereof when the tray is set to the service position. It is also possible to keep the through hole uncovered by removing the cover plate from the tray when desired.  
      In yet anther feature of the invention, the storage container is made of a flexible container, and the height of the flexible container from the upper opening to the bottom of the flexible container is made smaller than the height of the tray compartment from an upper end thereof to the opening of the flexible container.  
      This arrangement is advantageous in that the bottom of the flexible container would not project from the tray compartment beyond the upper end thereof when the tray is stowed in the tray compartment with the storage container made of the flexible container attached to the tray. Also, this arrangement serves to effectively prevent the bottom of the storage container from being caught between the upper end of the tray compartment and the bottom of the seat cushion.  
      Another seat unit of the present invention includes a seat cushion, a tray compartment located under the seat cushion, and a tray which is made storable in the tray compartment. In this seat unit, the seat cushion is supported in such a manner that the seat cushion can be moved between a first position at which the top side of the tray compartment is exposed and a second position at which the top side of the tray compartment is closed, and the tray can be moved between a storage position at which the tray is stored in the tray compartment and a service position at which the tray is located on one side of the seat cushion.  
      In this structure, the tray stowed in the storage position can be folded out to the service position located on one side of the seat cushion with the top side of the tray compartment exposed by swinging up the seat cushion, so that the tray can be used as a platform for holding various articles when necessary. When it is not necessary to use the tray, the tray can be stowed back to the storage position located under the seat cushion so that a free space is created on one side of the seat cushion to provide an improved walk-through capability for passengers.  
      This application is based on Japanese Patent Application Nos. 2003-413187 and 2004-262224 filed in Japan on Dec. 11, 2003 and Sep. 09, 2004, respectively, the contents of which are hereby incorporated by reference.  
      Although the present invention has been fully described by way of example with reference to the accompanying drawings, it,is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention hereinafter defined, they should be construed as being included therein.