Abstract:
An object of the present invention is to suppress rise in running resistance with increases in weight of a transport vehicle group, and prevent higher energy consumption and manufacturing cost. A transport device transports a transport vehicle ( 1 ) carrying an article (E) along a transport path including a curved path and forms a continuous floor (B) on the transport vehicle ( 1 ) in the entire or partial transport path. The transport device includes: running rails (R) that are laid along the transport path to support running wheels ( 4, 5 , and  6 ) of the transport vehicle ( 1 ); guide rails that guide the transport vehicle ( 1 ) along the transport path; a drive unit that drives the transport vehicle ( 1 ); and a water way (WW) that is formed along the transport path to reserve water (W).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a transport device that transports non-self-propelled transport vehicles carrying articles along a transport path including a curved path and forms a continuous floor on the transport vehicles in the entire or partial transport path. 
       BACKGROUND ART 
       [0002]    According to one transport device that can form a continuous work floor (work plane) on which a worker rides to perform work while transporting transport vehicles carrying articles along a transport path, front and back transport vehicles (1 and 1) are coupled together by vehicle coupling units (vehicle coupling means (9), coupling start means (10), and decoupling means (11)) and are transported at a constant speed by a pushing drive means (5A) in a straight work line (pushing run section (3)) where the ends of the transport vehicles (1) are in abutment with each other to form a continuous work floor, and the transport vehicle (1) having exited out of the work line is decoupled and transported at a higher speed by a high-speed drive means (5C) in a return line (high speed run section (4)) for returning the transport vehicle (1) having exited out of the work line to the entrance of the work line (for example, refer to Patent Document 1). 
         [0003]    According to another transport device, the transport vehicles (movable bodies (10)) are coupled together by a coupling unit (30) at the front and back parts opposed to each other so as to be capable of relative rotation in the lateral direction, a train-like endless continuous body (90) is formed from a transport vehicle group (moving body (10) group) and a coupling unit (30) group, and the endless continuous body (90) is driven by a feed unit (50) (for example, refer to Patent Document 2). 
         [0004]    According to still another transport device, transport vehicles (pallets (2)) are divided into a plurality of sections relative to the transport direction, the divided transport vehicles (divided pallets (2A, 2B, and 2C)) are movably coupled together in a horizontal plane, and the transport vehicles are transported in a free flow system in which, when the following transport vehicle abuts with the preceding transport vehicle, the following transport vehicle pushes the preceding transport vehicle (for example, refer to Patent Document 3). 
         [0005]    According to still another transport device, each of the transport vehicles (1) is composed of one or more vehicle bodies (1A and 1B) and coupled vehicle bodies (2A and 2B) that are positioned at the front or back side of the vehicle bodies (1A and 1B) in the transport direction and are coupled to the vehicle bodies (1A and 1B) so as to be capable of relative rotation around a vertical axis, the upper surfaces of the vehicle bodies (1A and 1B) and the upper surfaces of the coupled vehicle bodies (2A and 2B) are flush with each other, a coupling means (C) is provided to couple the transport vehicles (1 and 1) positioned at the front and back sides in the transport direction, the plurality of transport vehicles (1, 1, . . . ) is coupled by the coupling means (C) and is arranged as a transport vehicle group (A) in a transport path including a curved path (C1), a work line (L1) for performing parts assembly work while transporting the transport vehicle group (A) at a constant speed is formed with a work floor (B) composed of the upper surfaces of the vehicle bodies (1A and 1B) and the coupled vehicle bodies (2A and 2B), a return line (L2) is provided such that the transport vehicle (1) at the front end of the transport vehicle group (A) in the transport direction is separated and transported at a high speed and is coupled to the back end of the transport vehicle group (A), and an article (W) is unloaded from the single transport vehicle (1) separated from the transport vehicle group (A) and a new article (W) is loaded onto the same on the return line (L2) (for example, refer to Patent Document 4.). 
         [0006]    According to one wafer transport device that transports silicon wafers on a semiconductor production line, a liquid drive source (6) induces a flow of pure water (4) in a constant direction in a fluid path (5) as a circulation flow path, a float (3) carrying a wafer carrier (2) storing silicon wafers (1, 1, . . . ) and floating on the pure water (4) is moved by the flow along the fluid path (5), the float (3) is stopped by float stoppers (7a and 7b) in the vicinity of manufacturing devices (9a and 9b), and the wafer carrier (2) is transferred from the float (3) to the manufacturing devices (9a and 9b) and is transferred from the manufacturing devices (9a and 9b) to the float (3) by manipulators (8a and 8b) (for example, refer to Patent Document 5). 
       CITATION LIST 
     Patent Literatures 
       [0007]    Patent Document 1: JP-A No. 2006-117079 
         [0008]    Patent Document 2: JP-A No. H08-282481 
         [0009]    Patent Document 3: JP-A No. 2007-112605 
         [0010]    Patent Document 4: JP-A No. 2013-107731 
         [0011]    Patent Document 5: JP-A No. 863-102238 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0012]    The transport device as described in Patent Document 1 is configured to decouple the transport vehicle and transport the same at a high speed by the high-speed drive means on the line other than the straight work line (return line), and no work floor (work plane) on which the worker rides to perform work can be formed on the line other than the straight work line, thereby leading to degradation in work efficiency and space efficiency. 
         [0013]    The transport device as described in Patent Document 2 is configured to drive the entire train-like endless continuous body by the feed unit, and it is thus necessary to stop the entire endless continuous body to load and unload the articles on and from the transport vehicles with degradation in work efficiency. 
         [0014]    The transport device as described in Patent Document 3 is configured in the free flow system in which the preceding and following transport vehicles are not coupled but the following transport vehicle pushes the preceding transport vehicle, and a gap may be produced between the preceding and following transport vehicles. Accordingly, it is hard to form reliably the continuous work floor (work plane) on which the worker rides. 
         [0015]    In contrast to the foregoing devices, according to the transport device as described in Patent Document 4, each of the transport vehicles is composed of one or more vehicle bodies and coupled vehicle bodies that are positioned at the front or back side of the vehicle bodies in the transport direction and are coupled to the vehicle bodies so as to be capable of relative rotation around the vertical axis, and the upper surfaces of the vehicle bodies and the upper surfaces of the coupled vehicle bodies are approximately flush with each other. This makes it possible to form the continuous work floor on which the worker rides to perform parts assembly work, from the upper surfaces of the vehicle body composed of the transport vehicle group by coupling the plurality of transport vehicles via the coupling means and the upper surfaces of the coupled vehicle bodies, and it is also possible to arrange the transport vehicle group in the transport path including the curved path. 
         [0016]    Therefore, the worker is allowed to perform the parts assembly work even in the curved path with improvement in work efficiency and space efficiency. 
         [0017]    Further, the articles are unloaded from and loaded onto the single transport vehicle separated from the transport vehicle group on the return line. This eliminates the need to stop the transport vehicle group on the work line at the time of loading and unloading of the articles, and allows the worker to perform work while the transport vehicle group is transported at a constant speed on the work line with further improvement in work efficiency. 
         [0018]    Moreover, the preceding and following transport vehicles in the transport vehicle group are coupled by the coupling means on the work line and no gap is produced between the preceding and following transport vehicles even with fluctuation in the transport speed. This makes it possible to form reliably the continuous work floor (work plane) on which the worker rides. 
         [0019]    The transport device as described in Patent Document 4 has the foregoing features. However, the transport device is configured to include the transport vehicle group formed by coupling the plurality of transport vehicles via the coupling means and the large work floor on the transport vehicle group. Accordingly, the weight of the transport vehicle group becomes heavier to increase running resistance, and it is necessary to add large thrust at the time of driving by the drive unit. 
         [0020]    Therefore, the drive unit needs to be large in capacity, which causes the problem of increased energy consumption. 
         [0021]    Further, to drive the transport vehicle group by a friction-type drive unit, for example, it is necessary to press a friction roller strongly against the friction surface of the transport vehicle. Accordingly, the frame of the transport vehicle needs to be enhanced in strength with increase in manufacturing costs and the rubber of the friction roller surface may be deteriorated at earlier stages by breakage, deformation, or separation. 
         [0022]    The foregoing problems also exist in the transport devices as described in Patent Documents 1 to 3. 
         [0023]    The transport device as described in Patent Document 5 is configured to transport the float by the flow of pure water in the water way induced by the liquid drive source in the constant direction. Accordingly, the drive system includes a few sliding parts, and therefore dust is unlikely generated at the drive system and the wafer is not contaminated even if the pure water is scattered. This improves the yield of the semiconductor production line. 
         [0024]    However, when the float is transported by the water flow, it is difficult to keep constant the transport speed. Accordingly, this configuration cannot be applied to the work line on which the worker performs work while the transport vehicle group constituting the work floor is transported at a constant speed. 
         [0025]    Further, to transport an article long in the transport direction (travelling direction), it is necessary to lengthen the float in the transport direction and increase the curvature radius of the curved path (corner) with limitation on the layout of the water way. 
         [0026]    In view of the foregoing circumstances, an object of the present invention is to provide a transport device that transports non-self-propelled transport vehicles carrying articles along a transport path including a curved path and forms a continuous floor on the transport vehicles in the entire or partial transport path. The transport device can suppress increase in running resistance due to rise in weight of the transport vehicle group and suppress increase in energy consumption and manufacturing costs, thereby to prevent earlier-stage degradation of the rubber of the friction roller surface due to breakage, deformation, or separation at the time of driving by the friction-type drive unit. 
       Solution to Problem 
       [0027]    To solve the foregoing problems, a transport device according to the present invention transports a non-self-propelled transport vehicle carrying an article along a transport path including a curved path and forms a continuous floor on the transport vehicle in the entire or partial transport path. The transport device includes: running rails that are laid along the transport path to support running wheels of the transport vehicle; guide rails that guide the transport vehicle along the transport path; a drive unit that drives the transport vehicle; and a water way that is formed along the transport path to reserve water, wherein the transport vehicle is formed such that a plurality of frame bodies with upper surfaces approximately flush with each other is coupled together so as to be bendable relatively in the horizontal direction, and a float body partially or entirely immersed in the water reserved in the water way is fixed to a lower part of each or any of the frame bodies (Claim  1 ). 
         [0028]    According to this configuration, the transport vehicle is formed by coupling the plurality of frame bodies so as to be bendable relatively in the horizontal direction and the float body is fixed to the lower part of each or any of the frame bodies. The plurality of frame bodies bend in the horizontal direction along the curved path and the float body fixed to the lower part of the frame body moves in the water way along the curved path. 
         [0029]    Therefore, even when an article longer in the transport direction is to be transported, it is not necessary to increase the curvature radius of the curved path, without limitation on the layout of the transport path (water way) including the curved path. 
         [0030]    Further, the transport vehicle is formed by coupling the plurality of frame bodies with the upper surfaces approximately flush with each other so as to be bendable relatively in the horizontal direction. Accordingly, the worker can ride on the upper surface of the vehicle to perform work even in the curved path, with improvement in work efficiency and space efficiency. 
         [0031]    Furthermore, the transport vehicle is driven by the drive unit, which allows the transport vehicle to be transported at a constant speed. This achieves formation of the work line on which the worker can perform work while the transport vehicle forming the continuous floor is transported at a constant speed. 
         [0032]    Moreover, although the formation of the continuous floor leads to increase in the weight of the vehicle, the float body is fixed to the lower part of each or any of the frame bodies and is immersed in the water reserved in the water way. Accordingly, the load of the vehicle on the running rails becomes smaller due to the buoyancy of the float body. 
         [0033]    Therefore, the running resistance between the running wheels of the vehicle and the running rails is reduced to decrease thrust necessary for driving the vehicle. This results in reduction of energy consumption. 
         [0034]    It is preferred that the transport vehicle include a friction surface, and the drive unit driving the transport vehicle is a friction-type drive unit including a friction roller to be in abutment with the friction surface (Claim  2 ). 
         [0035]    According to this configuration, it is possible to reduce the load of the vehicle acting on the running rails due to the buoyancy of the float body and decrease thrust necessary for driving the vehicle as described above. Thus, even though the transport vehicle includes the friction surfaces and the drive unit driving the transport vehicle is a friction-type drive unit including a friction roller to be in abutment with the friction surfaces, it is possible to make the pressing force of the friction roller relatively small. This causes no increase in manufacturing costs for improving the strength of the frame bodies for the transport vehicle or no earlier-stage degradation of the rubber of the friction roller surface due to breakage, deformation, or separation during driving by the friction-type drive unit. 
         [0036]    It is preferred that a guided member drooping from an article support base supporting the article is supported in an ascendible and descendible manner by a guiding member provided at one of the frame bodies, and the float body partially or entirely immersed in the water reserved in the water way is fixed to the guided member positioned under the guiding member (Claim  3 ). 
         [0037]    According to this configuration, the guided member drooping from the article support base is supported in an ascendible and descendible manner by the guiding member and the float body is fixed to the guided member. Thus, in the state in which the article support base does not support the article, the guided member and the article support base ascend due to the buoyancy of the float body, and the load of the article support base does not act on the transport vehicle. 
         [0038]    Further, in the state in which the article support base supports the article, the article support base, the guided member, and the float body descend due to the load of the article, the float body is more immersed in the water with increased buoyancy, and thus the force acting on the transport vehicle due to the load of the article, the article support base, and the guided member becomes smaller. 
         [0039]    Therefore, it is possible to lessen the strength of the vehicle and decrease the running resistance between the running wheels of the vehicle and the running rails, thereby reducing thrust necessary for driving the vehicle with lower energy consumption. 
         [0040]    It is preferred that the transport device includes a height holding means that, in the state in which the article support base supports the article, holds the height of the article support base relative to the frame bodies at a constant value (Claim  4 ). 
         [0041]    According to this configuration, in the state in which the article support base supports the article, the article support base, the guided member, and the float body descend due to the load of the article, and the float body is more immersed in the water with increased buoyancy. The height holding means holds the height of the article support base relative to the frame bodies at a constant value while the buoyancy is about to match with the load of the article, the article support base, the guided member, and the float body. 
         [0042]    Therefore, it is possible to suppress the load of the article, the article support base, the guided member, and the float body acting on the transport vehicle and reduce the running resistance between the running wheels of the vehicle and the running rails. In addition, when the worker rides on the continuous floor to perform work, the height of the article is uniform relative to the floor. Accordingly, there is no deterioration in workability even if the water in the water way ruffles and shakes the float body in the vertical direction. 
         [0043]    It is preferred that a work line is configured such that a plurality of the transport vehicles is coupled together by a coupling means to form a transport vehicle group and the transport vehicle group is arranged in the transport path including the curved path, and the worker rides on an upper surface of the transport vehicle group as a work floor to perform work while the transport vehicle group is transported at a constant speed, a return line is provided such that the transport vehicle at the front end of the transport vehicle group in the transport direction is separated and transported at a high speed and is coupled to the back end of the transport vehicle group, and, on the return line, the article is unloaded from the single transport vehicle separated from the transport vehicle group and a new article is loaded onto the same (Claim  5 ). 
         [0044]    According to this configuration, the plurality of transport vehicles can be coupled together by the coupling means to form the transport vehicle group, and the worker can perform work on the upper surface of the transport vehicle group as the work floor, and the worker can unload and load the articles from and onto the transport vehicle separated from the front end of the transport vehicle group in the transport direction. This eliminates the need to stop the transport vehicle group on the work line for unloading and loading the articles with increased work efficiency. 
         [0045]    It is preferred that a section between the pair of frame bodies adjacent to each other at the front and back sides of the transport direction is formed in an arc-shaped convex portion at one side and in an arc-shaped concave portion at the other side in a plane view, the curvature radiuses of the arc-shaped convex portion and the arc-shaped concave portion are approximately identical, and the center of rotation around which the pair of frame bodies bends relatively in the horizontal direction is approximately identical to the centers of curvatures of the arc-shaped convex portion and the arc-shaped concave portion (Claim  6 ). 
         [0046]    According to this configuration, the space between the pair of frame bodies adjacent to each other at the front and back sides of the transport direction is formed in the arc-shaped convex portion at one side and in the arc-shaped concave portion at the other side in a plane view, the curvature radiuses of the arc-shaped convex portion and the arc-shaped concave portion are approximately identical, and the center of rotation around which the pair of frame bodies bends relatively in the horizontal direction is approximately identical to the centers of curvatures of the arc-shaped convex portion and the arc-shaped concave portion. Accordingly, the gap between the pair of frame bodies adjacent to each other at the front and back sides of the transport direction is smaller and is not widened even when the pair of frame bodies bends relatively in the horizontal direction. 
         [0047]    It is preferred that one of the front end and the back end of the transport vehicle is set as the arc-shaped convex portion and the other is set as the arc-shaped concave portion, the coupling means coupling the transport vehicles positioned at the front and back sides of the transport direction is composed of an arc-shaped guide groove formed in the arc-shaped convex portion at the coupling side of the transport vehicle positioned at the front and back sides of the transport direction and an engagement body for engagement with the arc-shaped guide groove provided at the arc-shaped concave portion at the coupling side of the same such that they are engageable with each other into a coupled state and are disengageable from each other into a decoupled state, and the center of curvature of the arc-shaped guide groove is approximately identical to the center of curvature of the arc-shaped convex portion (Claim  7 ). 
         [0048]    It is also preferred that one of the front end and the back end of the transport vehicle is set as the arc-shaped convex portion and the other is set as the arc-shaped concave portion, the coupling means coupling the transport vehicles positioned at the front and back sides of the transport direction is composed of an arc-shaped guide groove formed in the arc-shaped concave portion at the coupling side of the transport vehicle positioned at the front and back sides of the transport direction and an engagement body for engagement with the arc-shaped guide groove provided at the arc-shaped convex portion at the coupling side of the same such that they are engageable with each other into a coupled state and are disengageable from each other into a decoupled state, and the center of curvature of the arc-shaped guide groove is approximately identical to the center of curvature of the arc-shaped concave portion (Claim  8 ). 
         [0049]    According to these configurations, one of the front end and the back end of the transport vehicle is set as the arc-shaped convex portion and the other is set as the arc-shaped concave portion, a coupling means coupling the transport vehicles positioned at the front and back sides of the transport direction is composed of an arc-shaped guide groove formed in the arc-shaped convex portion (concave portion) at the coupling side of the transport vehicle positioned at the front and back sides of the transport direction and an engagement body for engagement with the arc-shaped guide groove provided at the arc-shaped concave portion (convex portion) at the coupling side of the same such that they are engageable with each other into a coupled state and are disengageable from each other into a decoupled state, and the center of curvature of the arc-shaped guide groove is approximately identical to the center of curvature of the arc-shaped convex portion (concave portion). Accordingly, in the coupled state in which the transport vehicles positioned at the front and back sides of the transport direction are coupled together by the coupling means, the gap between the transport vehicles is small and is not widened even when the front and back transport vehicles bend relatively in the horizontal direction. 
         [0050]    Therefore, the continuous floor can be obtained with little gap even in the curved path, which improves workability and causes no risk that the worker has their legs caught in the gap. 
         [0051]    In addition, the front and back transport vehicles are coupled together by the coupling means, and no gap is produced between the front and back transport vehicles even with variations in the transport speed and the like. Accordingly, it is possible to form reliably the continuous work floor on which the worker rides. 
         [0052]    Further, the coupling means is composed of the arc-shaped guide groove and the engagement body, and the center of curvature of the arc-shaped guide groove and the center of curvature of the arc-shaped convex portion (concave portion) are approximately identical. Accordingly, the coupling means is easy to fabricate, and the simply-structured coupling means can bring the transport vehicles into the coupled state and the decoupled state in a stable and reliable manner. 
         [0053]    It is preferred that the transport device includes a water flow generation unit that generates a forward water flow in the transport direction in the water reserved in the water way to apply thrust to the transport vehicle via the float body in the transport direction (Claim  9 ). 
         [0054]    According to this configuration, the water flow generation unit applies thrust to the transport vehicles via the float bodies and the transport vehicles are driven by the thrust, which reduces the drive force of the drive unit necessary for driving the transport vehicles. 
       Advantageous Effects of Invention 
       [0055]    As described above, according to the transport device in the present invention, the following significant advantages can be produced: 
         [0056]    (A) Even when an article long in the transport direction is to be transported, it is not necessary to increase the curvature radius of the curved path, and there is no limitation on the layout of the transport path (water way) including the curved path. 
         [0057]    (B) The worker can ride on the upper surface of the vehicle to perform work even in the curved path with improvement in work efficiency and space efficiency. 
         [0058]    (C) The transport vehicles can be transported at a constant speed, and it is possible to form a work line such that the worker performs work while the transport vehicles constituting the continuous floor are transported at a constant speed. 
         [0059]    (D) The running resistance between the running wheels of the vehicle and the running rails can be reduced to decrease thrust necessary for driving the vehicle and cut energy consumption. In addition, even though the drive unit driving the transport vehicle is a friction-type drive unit, there is no increase in manufacturing costs for improving the strength of the frame bodies for the transport vehicle or no earlier-stage degradation of the rubber of the friction roller surface due to breakage, deformation, or separation. 
         [0060]    (E) The continuous work floor with little gap can be obtained even in the curved path to improve workability and cause no risk that the worker has their legs caught in the gap. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0061]      FIG. 1  is a diagram schematically illustrating a layout of a transport device according to an embodiment of the present invention; 
           [0062]      FIG. 2  is a front view of a transport vehicle according to the embodiment of the present invention; 
           [0063]      FIG. 3  is a vertical cross-sectional view of the transport vehicle as seen from the back side; 
           [0064]      FIG. 4  is a plane view of the transport vehicle in a curved path on a work line; 
           [0065]      FIG. 5  is a plane view of the transport vehicle in a straight path on a return line; 
           [0066]      FIG. 6  is a bottom view of the transport vehicle; 
           [0067]      FIG. 7  include vertical front views describing operations of a coupling means that couples a transport vehicle (following vehicle) approaching from the back side to a transport vehicle (preceding vehicle) at the back end of a transport vehicle group,  FIG. 7( a )  illustrates the state in which the following vehicle approaches the preceding vehicle and an inclined surface of a coupling frame of the following vehicle is in abutment with a lift roller of the preceding vehicle,  FIG. 7( b )  illustrates the state in which the following vehicle further approaches the preceding vehicle and the coupling frame is lifted and swung upward by the lift roller,  FIG. 7( c )  illustrates the state in which the following vehicle further approaches the preceding vehicle and the coupling frame is swung more upward, and  FIG. 7( d )  illustrates the coupling complete state in which the following vehicle further approaches the preceding vehicle, the coupling frame is swung downward, and the lift roller enters in an arc-shaped guide groove; 
           [0068]      FIG. 8  is a vertical front view describing the operation of decoupling by the coupling means; 
           [0069]      FIG. 9  is a front view of a configuration example of a height holding means; 
           [0070]      FIG. 10  is a bottom view of a modification example of the transport vehicle; 
           [0071]      FIG. 11  includes vertical front views for describing operations of a coupling means that couples a transport vehicle (following vehicle) approaching from the back side to a transport vehicle (preceding vehicle) at the back end of a transport vehicle group composed of a modification example of the transport vehicles,  FIG. 11( a )  illustrates the state in which the following vehicle approaches the preceding vehicle,  FIG. 11( b )  illustrates the state in which the following vehicle further approaches the preceding vehicle and a coupling frame is lifted and swung upward by a lift roller, and  FIG. 11( c )  illustrates the coupling complete state in which the following vehicle further approaches the preceding vehicle, the coupling frame is swung downward, and the lift roller enters in an arc-shaped guide groove; and 
           [0072]      FIG. 12  is a vertical front view describing the operation of decoupling by the coupling means. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0073]    Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments illustrated in the accompanying drawings and includes all of embodiments satisfying the requirements described in the claims. 
         [0074]    The side in the direction of transporting articles (see arrow F in the drawings) will be designated as front side, and the side in the reverse direction as a back side. Views seen from the left side will be designated as front views. 
         [0075]    As illustrated in the schematic layout diagram of  FIG. 1 , a transport device according to an embodiment of the present invention transports non-self-propelled transport vehicles  1 ,  1 , . . . carrying articles E by feed units T 1 , T 2 , and T 3  as friction roller-type drive units along an endless transport path composed of straight paths S 1  and S 2  and curved paths C 1  and C 2 . 
         [0076]    The transport device arranges a transport vehicle group A formed by coupling front and back transport vehicles  1  and  1  by a coupling means C (see the vertical front view of  FIG. 7 ) described later in the transport path including the curved path C 1 , and has a work line L 1  such that a continuous work floor (work plane) B (see the front views of  FIGS. 2 and 9 ) on which the worker rides to perform work is formed on the transport vehicles  1 ,  1 , . . . in part of the transport path. As illustrated in the vertical cross-sectional view as seen from the back side of  FIG. 3 , the work floor B is flush with a floor surface G. 
         [0077]    In addition, a return line L 2  is formed by part of the straight path S 2 , the curved path C 2 , and part of the straight path S 1  such that the transport vehicle  1  at the front end of the transport vehicle group A is separated from the transport vehicle group A, and the separated transport vehicle  1  is transported at a high speed and coupled to the back end of the transport vehicle group A. 
         [0078]    Further, the return line L 2  includes a loading station ST 1  where the articles E are loaded and an unloading station ST 2  where the articles E are unloaded. At the unloading station ST 2 , the articles E are unloaded from the single transport vehicle  1  separated from the transport vehicle group A, and at the loading station ST 1 , new articles E are loaded onto the empty single transport vehicle  1 . 
         [0079]    Furthermore, a water way WW reserving water W is provided under the transport vehicles  1  along the transport path. Float bodies F 1  to F 4  illustrated in the front view of  FIG. 2  are immersed in the water W to generate buoyancy acting on the transport vehicles  1 . 
         [0080]    The transport vehicle group A is transported by a constant-speed transport feed unit T 1 . Specifically, the transport vehicle  1  at the front end is driven by press-fitting friction rollers  21 , . . . of the constant-speed transport feed unit T 1  to the side surface of the transport vehicle  1  at the front end (see a driven surface H in  FIGS. 3 to 6 ) while receiving reaction force by backup rollers  22 , . . . of the constant-speed transport feed unit T 1 , thereby to tow the following transport vehicles  1 ,  1 , . . . and transport the transport vehicle group A in an integrated manner at a constant speed. 
         [0081]    By bringing a friction roller  21  of the brake feed unit T 3  slightly lower in speed than the constant-speed transport feed unit T 1  into press-fit with the side surface (driven surface H) of the transport vehicle  1  at the back end of the transport vehicle group A, it is possible to produce the effect that tension force acts on the entire transport vehicle group A to prevent occurrence of rattle among the transport vehicles  1  in the vehicle group A. 
         [0082]    Alternatively, the constant-speed transport feed unit T 1  may be provided at the back end of the transport vehicle group A to drive the vehicle group A forward, and the brake feed unit T 3  may be provided at the front end of the transport vehicle group A. 
         [0083]    Further, as described above, the single transport vehicle  1  separated from the transport vehicle group A is transported by the high-speed transport feed unit T 2  bringing the friction roller  21  into press-fit with the side surface (driven surface H) of the transport vehicle  1 . At the loading station ST 1  and the unloading station ST 2 , the transport vehicle  1  is stopped at a predetermined position to load and unload the articles E. 
         [0084]    Furthermore, when the transport vehicle  1  loaded with the new article E at the loading station ST 1  is to be transported at a high speed and coupled to the back end of the transport vehicle group A by the high-speed transport feed unit T 2 , the high-speed transport feed unit T 2  is shifted to low-speed operation to decelerate the transport vehicle  1  having been transported at a high speed and couple the same to the back end of the transport vehicle group A by the coupling means C. 
         [0085]    In this example, a water flow generation unit as an underwater pump with a discharge port may be provided at an appropriate position in the schematic layout illustrated in  FIG. 1  (for example, in the vicinity of the high-speed transport feed unit T 2  on the return line L 2 ) so that the water flow generation unit generates a forward water flow to assist the feed units T 1 , T 2 , and T 3  as drive units. 
         [0086]    In the case where the layout of the transport device does not constitute a closed circuit (endless path) as illustrated in  FIG. 1 , a water flow generation unit generating a water flow by a difference in height may be used instead of the water flow generation unit as an underwater pump. 
         [0087]    As illustrated in the front view of  FIG. 2 , the vertical cross-sectional view as seen from the back side of  FIG. 3 , the plane views of  FIGS. 4 and 5 , and the bottom view of  FIG. 6 , the transport vehicle  1  according to the embodiment of the present invention is composed of a vehicle body  2  with an article support base D supporting the article E, a front coupled vehicle body  3 A that is positioned at the front side of the vehicle body  2  and is coupled to the vehicle body  2  around a vertical axis so as to be capable of relative rotation, a back coupled vehicle body  3 B that is positioned at the back side of the vehicle body  2  and is coupled to the vehicle body  2  around the vertical axis so as to be capable of relative rotation, and others. The upper surface of the vehicle body  2  and the upper surfaces of the front coupled vehicle body  3 A and the back coupled vehicle body  3 B are approximately flush with each other. 
         [0088]    The vehicle body  2  is formed by fixing a frame member to the lower surface of a plate member with straight right and left sides and arc-shaped convex front and back sides (front and back end portions) and attaching running wheels  4 ,  4 , . . . to the front, back, right, and left of the frame body with the horizontal upper surface, such that the running wheels  4 ,  4 , . . . roll on right and left running rails R and R laid along the transport path. 
         [0089]    The front coupled vehicle body  3 A is formed by fixing a frame member to the lower surface of a plate member with straight right and left sides, an arc-shaped convex front side (front end portion), and an arc-shaped concave back side (back end portion), and attaching running wheels  5 ,  5 , . . . to the front, back, right, and left of the frame body with the horizontal upper surface, such that the running wheels  5 ,  5 , . . . roll on the running rails R and R. 
         [0090]    The back coupled vehicle body  3 B is formed by fixing a frame member to the lower surface of a plate member with straight right and left sides and arc-shaped concave front and back sides, and attaching running wheels  6 ,  6 , . . . to the front, back, right, and left of the frame body with the horizontal upper surface, such that the running wheels  6 ,  6 , . . . roll on the running rails R and R. 
         [0091]    The curvature radiuses of the arc-shaped convex portions and the arc-shaped concave portions are approximately identical. 
         [0092]    As illustrated in the plane views of  FIGS. 4 and 5  and the bottom view of  FIG. 6 , coupling rods  7  and  8  long in the front-back direction are fixed to the right and left at the back side of the lower surface of the frame member of the front coupled vehicle body  3 A, and they are protruded backward. Coupling rollers (horizontal rollers rotatable around the vertical axis)  7 A and  8 A as engagement bodies are attached to the upper sides of the back end portions of the coupling rods  7  and  8 . 
         [0093]    In addition, coupling rods  9  and  10  long in the front-back direction are fixed to the right and left of the lower surface of the frame member of the back coupled vehicle body  3 B, and they are protruded forward and backward. Coupling rollers (horizontal rollers rotatable around the vertical axis)  9 A and  10 A as engagement bodies are attached to the upper sides of the front end portions of the coupling rods  9  and  10 . Coupling rollers (horizontal rollers rotatable around the vertical axis)  9 B and  10 B as engagement bodies are attached to the upper side of the back portion of the coupling rod  9  and the upper side of the back end portion of the coupling rod  10 . 
         [0094]    The coupling rod  9  is protruded more backward than the coupling rod  10 . Guide rollers (horizontal rollers rotatable around the vertical axis)  13 A and  13 B along a guide rail G 2  described later are attached to the lower side of the back end portion of the coupling rod  9 . 
         [0095]    Arc-shaped guide grooves  14 A and  14 B are formed on the insides (inner-diameter sides) of the arc-shaped convex portions at the front and back sides of the vehicle body  2 , and an arc-shaped guide groove  15  is formed on the inside (inner-diameter side) of the arc-shaped convex portion at the front side of the front coupled vehicle body  3 A. The centers of curvatures of the arc-shaped guide grooves  14 A,  14 B, and  15  are approximately identical to the centers of curvatures of the arc-shaped convex portions. 
         [0096]    The coupling rollers  7 A and  8 A at the back end portions of the coupling rods  7  and  8  of the front coupled vehicle body  3 A engage with the arc-shaped guide groove  14 A, and the coupling rollers  9 A and  10 A at the front end portions of the coupling rods  9  and  10  of the back coupled vehicle body  3 B engage with the arc-shaped guide groove  14 B. In this engagement state, the center of rotation around which the vehicle body  2  and the front coupled vehicle body  3 A bend relatively in the horizontal direction becomes approximately identical to the centers of curvatures of the arc-shaped convex portion at the front side of the vehicle body  2  and the arc-shaped concave portion at the back side of the front coupled vehicle body  3 A, and the center of rotation around which the vehicle body  2  and the back coupled vehicle body  3 B bend relatively in the horizontal direction becomes approximately identical to the centers of curvatures of the arc-shaped convex portion at the back side of the vehicle body  2  and the arc-shaped concave portion at the front side of the back coupled vehicle body  3 B. 
         [0097]    Therefore, the gap between the vehicle body  2  and the front coupled vehicle body  3 A and the gap between the vehicle body  2  and the back coupled vehicle body  3 B are small, and the gaps will not be widened even when the vehicle body  2  and the front coupled vehicle body  3 A and the vehicle body  2  and the back coupled vehicle body  3 B bend relatively in the horizontal direction. 
         [0098]    In the state in which the front and back transport vehicles  1 ,  1 , . . . are coupled together as illustrated in  FIG. 4 , the coupling rollers  9 B and  10 B at the back portions of the coupling rods  9  and  10  of the back coupled vehicle body  3 B of the preceding vehicle engage with the arc-shaped guide groove  15  of the front coupled vehicle body  3 A of the following vehicle. In this engagement state, the center of rotation around which the back coupled vehicle body  3 B of the preceding vehicle and the front coupled vehicle body  3 A of the following vehicle bend relatively in the horizontal direction is approximately identical to the centers of curvatures of the arc-shaped concave portion at the back side of the back coupled vehicle body  3 B of the preceding vehicle and the arc-shaped convex portion at the front side of the front coupled vehicle body  3 A of the following vehicle. 
         [0099]    Therefore, in the state in which the transport vehicles  1  and  1  positioned at the front and back of the transport direction are coupled together by the coupling means C, the gap between the vehicles  1  and  1  is small and will not be widened even when the front and back transport vehicles  1  and  1  bend relatively in the horizontal direction. 
         [0100]    Accordingly, the continuous work floor B with little gap can be obtained even in the curved path C 1  to improve workability and eliminate the risk that the worker has their legs caught in the gap. 
         [0101]    In the foregoing description, the transport vehicle  1  is composed of the vehicle body  2 , the front coupled vehicle body  3 A, and the back coupled vehicle body  3 B, that is, the transport vehicle  1  is formed by coupling the three frame bodies capable of bending relatively in the horizontal direction. However, the transport vehicle  1  in the present invention is merely required to be formed such that a plurality of frame bodies with the upper surfaces approximately flush with each other is coupled together so as to be capable of bending relatively in the horizontal direction. 
         [0102]    In the foregoing description, the front side (front end portion) of the transport vehicle  1  is an arc-shaped convex portion and the back side (back end portion) of the same is an arc-shaped concave portion. Alternatively, the front side may be an arc-shaped concave portion and the back side may be an arc-shaped convex portion. 
         [0103]    As illustrated in the vertical cross-sectional view as seen from the back side of  FIG. 3  and the plane view of  FIG. 4 , in the transport vehicle group A with the front and back transport vehicles  1  and  1  coupled on the work line L 1 , guide rollers  11 A and  11 B provided at the front and back of the right side of the lower surface of the vehicle body  2  and guide rollers  12 A and  12 B provided at the front of the right side of the lower surface of the front coupled vehicle body  3 A sandwich a guide rail G 1  laid at the right side of the transport path, and the transport vehicles  1 ,  1 , . . . (transport vehicle group A) are guided by the guide rail G 1 . 
         [0104]    In addition, as illustrated in the plane view of  FIG. 5 , the guide rollers  11 A and  11 B provided at the front and back of the right side of the lower surface of the vehicle body  2  and the guide rollers  12 A and  12 B provided at the front of the right side of the lower surface of the front coupled vehicle body  3 A sandwich the guide rail G 1 , and guide rollers  13 A and  13 B at the back end portion of the coupling rod  9  of the back coupled vehicle body  3 B sandwich the guide rail G 2  laid at the left side of the transport path, and therefore the single transport vehicle  1  separated from the transport vehicle group A on the return line L 2  is guided by the guide rails G 1  and G 2 . 
         [0105]    As illustrated in the front view of  FIG. 2  and the plane views of  FIGS. 4  and  5 , the float body F 1  is fixed to the lower part of the frame body of the vehicle body  2 , the float body F 2  is fixed to the lower part of the frame body of the front coupled vehicle body  3 A, and the float body F 3  is fixed to the lower part of the frame body of the back coupled vehicle body  3 B. The float bodies F 1 , F 2 , and F 3  are partially or entirely immersed in the water reserved in the water way WW, and the load of the vehicle  1  acting on the running rails R and R becomes smaller due to the buoyancy of the float bodies F 1 , F 2 , and F 3 . 
         [0106]    Therefore, the running resistance between the running wheels  4 , . . . ,  5 , . . . ,  6 , . . . of the vehicles  1  and the running rails R and R is reduced to decrease thrust necessary for driving the vehicle  1  and cut energy consumption. 
         [0107]    In this example, the immersed volumes of the float bodies F 1 , F 2 , and F 3  are changed according to the weights of the frame body of the vehicle body  2 , the frame body of the front coupled vehicle body  3 A, and the frame body of the back coupled vehicle body  3 B to allow the appropriate buoyancy to act according to the weights of the frame bodies. Specifically, the immersed volume of the float body F 1  of the heaviest vehicle body  2  is made largest, the immersed volume of the float body F 3  of the lightest back coupled vehicle body  3 B is made smallest, and the immersed volume of the float body F 2  of the front coupled vehicle body  3 A heavier than the back coupled vehicle body  3 B and lighter than the vehicle body  2  is made larger than the immersed volume of the float body F 3  and smaller than the immersed volume of the float body F 1 . 
         [0108]    By adjusting the immersed volumes of the float bodies F 1 , F 2 , and F 3 , the loads of the frame body of the vehicle body  2 , the frame body of the front coupled vehicle body  3 A, and the frame body of the back coupled vehicle body  3 B acting on the running rails R and R can be uniformed. This minimizes the frictional resistance during running of the transport vehicle  1 . 
         [0109]    As illustrated in the front view of  FIG. 2 , the vertical cross-sectional view as seen from the back side of  FIG. 3 , the plane views of  FIGS. 4 and 5 , and the front view of  FIG. 9 , front and back rods  19  and  19  as guided members drooping from the article support base D supporting the article E are supported in an ascendible and descendible manner by front and back guiding members  20  and  20  provided at the frame body of the vehicle body  2 . Float bodies F 4  and F 4  partially or entirely immersed in the water W reserved in the water way WW are fixed to the rods  19  and  19  under the guiding members  20  and  20 . 
         [0110]    Therefore, in the state in which the article support base D does not support the article E (shown by virtual lines in  FIG. 9 ), the rods  19  and  19  and the article support base D are raised by the buoyancy of the float bodies F 4  and F 4  and the load of the article support base D does not act on the vehicle body  2  (transport vehicle  1 ). 
         [0111]    In the state in which the article support base D supports the article E (shown by solid lines in  FIG. 9 ), the article support base D, the rods  19  and  19 , and the float bodies F 4  and F 4  are lowered under the load of the article E and the immersed amounts of the float bodies F 4  and F 4  increase to enhance the buoyancy and decrease the force acting on the vehicle body  2  (transport vehicle  1 ) under the loads of the article E, the article support base D, and the rods  19  and  19 . 
         [0112]    Therefore, it is possible to lessen the strength of the vehicle  1  and decrease the running resistance between the running wheels  4 , . . . ,  5 , . . . ,  6 , . . . of the vehicle  1  and the running rails R and R, thereby reducing thrust necessary for driving the vehicle  1  with lower energy consumption. 
         [0113]    Further, in the state in which the article support base D supports the article E (shown by the solid lines in  FIG. 9 ), the lower surface of the article support base D is in abutment with upper surfaces  20 A and  20 A of the guiding members  20  and  20  and the height of the article support base D (article E) is held at a constant value relative to the transport vehicle  1  while the buoyancy of the float bodies F 4  and F 4  is about to match the loads of the article E, the article support base D, the rods  19  and  19 , and the float bodies F 4  and F 4 . 
         [0114]    By providing the height holding means that, in the state in which the article support base D supports the article E, holds the height of the article support base D (article E) at a constant value relative to the transport vehicle  1  (the frame bodies), the height of the article E is made constant relative to the work floor B on which the worker rides to perform work. Accordingly, there is no degradation in workability even when the water W in the water way WW ripples to shake the float bodies F 4  and F 4  in the vertical direction. 
         [0115]    The height holding means is not limited to the configuration in which the upper surfaces  20 A and  20 A of the guiding members  20  and  20  illustrated in  FIG. 9  bring into abutment with the lower surface of the article support base D to determine the lowest position of the article support base D. Alternatively, the article support base D may be provided with guide rollers such that the guide rollers are brought into contact with the guide rails laid on the ground to hold the height of the article support base D (article E) at a constant value. 
         [0116]    Next, a configuration example of the coupling means C will be described mainly with reference to the vertical front views for describing operation of  FIG. 7 . 
         [0117]    As illustrated in  FIGS. 2, 5, and 7 , a coupling frame  16  is attached to the front end portion of the front coupled vehicle body  3 A so as to be capable of swinging upward around a swinging shaft  16 B, and an inclined plane  16 A is formed on the lower surface at the front end edge of the coupling frame  16 . 
         [0118]    In addition, as illustrated in  FIGS. 5 and 7 , a lift roller  17  is attached to the tip of an arm protruding backward at the center of the back coupled vehicle body  3 B in the horizontal direction so as to be capable of rotation around a horizontal axis. 
         [0119]    Therefore, as illustrated in  FIG. 7( a ) , in the state in which the following vehicle  1 B is close to the preceding vehicle  1 A and the inclined plane  16 A of the coupling frame  16  of the following vehicle  1 B is in abutment with the lift roller  17  of the preceding vehicle  1 A, when the following vehicle  1 B further approaches the preceding vehicle  1 A as illustrated in  FIGS. 7( b ) and 7( c ) , the lift roller  17  of the preceding vehicle  1 A swings the coupling frame  16  of the following vehicle  1 B upward around the swinging shaft  16 B. 
         [0120]    Then, when the following vehicle  1 B further approaches the preceding vehicle  1 A as illustrated in  FIG. 7( d ) , the coupling frame  16  of the following vehicle  1 B swings downward and the lift roller  17  of the preceding vehicle  1 A enters into the arc-shaped guide groove  15 . In this state, the coupling rollers  9 B and  10 B of the preceding vehicle  1 A (for example, see  FIGS. 4 and 5 ) engage with the arc-shaped guide groove  15  of the following vehicle  1 B (for example, see  FIG. 5 ), and the following vehicle  1 B is coupled to the preceding vehicle  1 A. 
         [0121]    Next, a configuration example for decoupling the front and back vehicles by the coupling means C will be described. 
         [0122]    As illustrated in the vertical front view of  FIG. 8 , decoupling cam rails  18  and  18  (also see  FIG. 3 ) provided at predetermined positions lift operated rollers  16 C and  16 C of the coupling frame  16  of the following vehicle  1 B to open the front side of the lift roller  17  and the coupling rollers  9 B and  10 B of the preceding vehicle  1 A (at the front end of the transport vehicle group A in the transport direction), whereby the preceding vehicle  1 A is decoupled from the following vehicle  1 B. 
         [0123]    Accordingly, the preceding vehicle  1 A (at the front end of the transport vehicle group A in the transport direction) is driven by the high-speed transport feed unit T 2  to transport the preceding vehicle  1 A alone. 
         [0124]    When the front and back transport vehicles  1  and  1  are coupled by the coupling means C, no gap is produced between the front and back transport vehicles  1  and  1  even with variations in the transport speed and the like, thereby forming reliably the continuous work floor B on which the worker rides. 
         [0125]    In addition, the coupling means C is composed of the arc-shaped guide groove  15  and the engagement bodies (coupling rollers  9 B and  10 B), and the center of curvature of the arc-shaped guide groove  15  is approximately identical to the center of curvature of the arc-shaped convex portion. Accordingly, the coupling means C is easy to fabricate, and the simply-structured coupling means C can bring the transport vehicles into the coupled state and the decoupled state in a stable and reliable manner. 
         [0126]    Next, modification examples of the transport vehicle  1  and the coupling means C will be described. 
         [0127]    In the bottom view of a modification example of the transport vehicle  1  of  FIG. 10 , the vertical front view for describing the operation of the coupling means of  FIG. 11 , and the vertical front view for describing the operation of decoupling by the coupling means of  FIG. 12 , the components with the same reference signs as those in  FIGS. 1 to 11  are identical or equivalent to the components illustrated in  FIGS. 1 to 11 . 
         [0128]    The modification example of the transport vehicle  1  illustrated in the bottom view of  FIG. 10  will be described below as compared to the transport vehicle  1  illustrated in the bottom view of  FIG. 6 . 
         [0129]    In the transport vehicle  1  of  FIG. 6 , the arc-shaped guide groove  15  is formed at the arc-shaped convex portion at the coupling side (front end portion) of the transport vehicle  1 . 
         [0130]    In contrast to this, in the transport vehicle  1  of  FIG. 10 , the arc-shaped guide groove  15  is formed at the arc-shaped concave portion at the coupling side (back end portion) of the transport vehicle  1 . In addition, in the transport vehicle  1  of  FIG. 10 , the center of curvature of the arc-shaped guide groove  15  is approximately identical to the center of curvature of the arc-shaped concave portion at the back end portion. 
         [0131]    In the transport vehicle  1  of  FIG. 6 , the coupling frame  16 , the inclined plane  16 A, the swinging shaft  16 B, and the operated rollers  16 C are provided at the front coupled vehicle body  3 A, and the lift roller  17  is attached to the tip of the arm protruding backward from the back coupled vehicle body  3 B. 
         [0132]    In contrast to this, in the transport vehicle  1  of  FIG. 10 , the coupling frame  16 , the inclined plane  16 A, the swinging shaft  16 B, and the operated rollers  16 C are provided at the back coupled vehicle body  3 B, and the lift roller  17  is attached to the tip of the arm protruding forward from the front coupled vehicle body  3 A. 
         [0133]    Further, in the transport vehicle  1  of  FIG. 6 , the coupling rods  9  and  10  long in the front-back direction are fixed to the back coupled vehicle body  3 B and are protruded forward and backward, the coupling rollers  9 A and  10 A as engagement bodies are attached to the upper sides of the front end portions of the coupling rods  9  and  10 , and the coupling rollers  9 B and  10 B as engagement bodies are attached to the upper side of the back portion of the coupling rod  9  and the upper side of the back end portion of the coupling rod  10 . 
         [0134]    In contrast to this, in the transport vehicle  1  of  FIG. 10 , the coupling rods  9  and  10  are fixed to the back coupled vehicle body  3 B and are protruded forward, and the coupling rollers  9 A and  10 A as engagement bodies are attached to the upper sides of the front end portions of the coupling rods  9  and  10 , the coupling rods  23  and  24  fixed to the front coupled vehicle body  3 A are protruded forward, and the coupling rollers  23 A and  24 A as engagement bodies are attached to the upper sides of the front end portions of the coupling rods  23  and  24 . 
         [0135]    Furthermore, in the transport vehicle  1  of  FIG. 6 , the guide rollers  13 A and  13 B along the guide rail G 2  are attached to the lower side of the back end portion of the coupling rod  9  protruding more backward than the coupling rod  10 . 
         [0136]    In contrast to this, in the transport vehicle  1  of  FIG. 10 , the guide rollers  13 A and  13 B along the guide rail G 2  are attached to the lower side of the back end portion of the coupling rod  9  protruding backward, as in the transport vehicle  1  of  FIG. 6 . 
         [0137]    According to the configuration of the transport device as described above, the vehicle body  2 , the front coupled vehicle body  3 A, and the back coupled vehicle body  3 B are coupled together so as to be capable of bending relatively in the horizontal direction to form the transport vehicle  1 , and the float bodies F 1 , F 2 , and F 3  are fixed to the lower parts of the frame bodies of the vehicle body  2 , the front coupled vehicle body  3 A, and the back coupled vehicle body  3 B. Accordingly, the vehicle body  2 , the front coupled vehicle body  3 A, and the back coupled vehicle body  3 B bend in the horizontal direction along the curved paths C 1  and C 2 , and the float bodies F 1 , F 2 , and F 3  fixed to the lower parts of the vehicle body  2 , the front coupled vehicle body  3 A, and the back coupled vehicle body  3 B move in the water way WW along the curved paths C 1  and C 2 . 
         [0138]    Therefore, even in the case of transporting the article E long in the transport direction, it is not necessary to increase the curvature radiuses of the curved paths C 1  and C 2  with no limitation on the layout of the transport path (water way WW) including the curved paths C 1  and C 2 . 
         [0139]    In addition, the vehicle body  2 , the front coupled vehicle body  3 A, and the back coupled vehicle body  3 B with the upper surfaces flush with one another are coupled together so as to be capable of bending relatively in the horizontal direction to form the transport vehicle  1 , and the worker can ride on the upper surface of the vehicle to perform work even in the curved path C 1  with improved work efficiency and space efficiency. 
         [0140]    Further, the load of the vehicle  1  acting on the running rails R and R is lessened by use of the buoyancy of the float bodies F 1 , F 2 , F 3 , and F 4  to reduce thrust necessary for driving of the vehicle  1 . Accordingly, even when the side surface (or any other surface) of the transport vehicle  1  includes a friction surface H and the drive unit for driving the transport vehicle  1  is a friction-type drive unit including a friction roller  21  to be in abutment with the friction surface H, the pressing force of the friction roller  21  can be made relatively small. Accordingly, there is no increase in manufacturing costs for enhancing the strength of the frame bodies of the transport vehicle  1  or no earlier-stage deterioration of the rubber of the surface of the friction roller  21  due to breakage, deformation, separation, or the like when being driven by the friction-type drive unit. 
         [0141]    Furthermore, in the configuration in which the water flow generation unit is provided to generate a forward water flow in the water W reserved in the water way WW and apply thrust to the transport vehicle  1  via the float bodies F 1 , F 2 , F 3 , and F 4 , the transport vehicle  1  can be driven by the thrust generated from the water flow to reduce the driving force of the feed units T 1 , T 2 , and T 3  as drive units for driving the transport vehicle  1 . 
         [0142]    In the foregoing description, the continuous work floor (work plane) B on which the worker rides to perform work is formed on the transport vehicles  1 ,  1 , . . . . However, the transport device in the present invention is also applicable to the transport path dedicated for transport without work processes. In the case of using the transport device in the present invention for the transport path dedicated for transport, not the continuous work floor on which the worker rides to perform work but a continuous floor is formed on the transport vehicles  1 ,  1 , . . . so that the worker or others rides on the continuous floor to traverse the transport path, for example. 
         [0143]    In the foregoing description, the work floor B is formed in some parts of the straight paths S 1  and S 2  and the curved path C 1 . Alternatively, the work floor B may be formed only in some parts of the straight paths S 1  and S 2  or may be formed only in some parts of the curved paths C 1  and C 2 . 
         [0144]    Further, in the foregoing description, the work floor B is formed in part of the transport path including the curved path C 1 . Alternatively, the work floor B may be formed in the entire transport path. This case produces the advantage that the worker can ride on the work floor B to perform work in the entire region (entire length) of the transport path. In this case, however, it is not possible to stop the individual vehicle  1  to load and unload the articles E (see the loading station ST 1  and the unloading station ST 2  illustrated in  FIG. 1 ). Accordingly, the articles E are loaded and unloaded in synchronization with the vehicle  1  moving at a constant speed or the articles E are loaded and unloaded while all the coupled vehicles  1 ,  1 , . . . are stopped concurrently. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         A Transport vehicle group 
         B Continuous work floor 
         C Coupling means 
         C 1 ,C 2  Curved path 
         D Article support base 
         E Article 
         F Transport direction 
         F 1 , F 2 , F 3 , and F 4  Float body 
         G Floor surface 
         G 1  and G 2  Guide rail 
         H Driven surface 
         L 1  Work line 
         L 2  Return line 
         R Running rail 
         S 1 ,S 2  Straight path 
         ST 1  Loading station 
         ST 2  Unloading station 
         T 1  Constant-speed transport feed unit (friction-type drive unit) 
         T 2  High-speed transport feed unit (friction-type drive unit) 
         T 3  Brake feed unit (friction-type drive unit) 
         W Water 
         WW Water way 
           1  Transport vehicle 
           1 A Preceding vehicle 
           1 B Following vehicle 
           2  Vehicle body (frame body) 
           3 A Front coupled vehicle body (frame body) 
           3 B Back coupled vehicle body (frame body) 
           4 ,  5 , and  6  Running wheel 
           7 ,  8 ,  9 , and  10  Coupling rod 
           7 A,  8 A,  9 A,  9 B,  10 A, and  10 B Coupling roller (engagement body) 
           11 A,  11 B,  12 A,  12 B,  13 A, and  13 B Guide roller 
           14 A,  14 B, and  15  Arc-shaped guide groove 
           16  Coupling frame 
           16 A Inclined plane 
           16 B Swinging shaft 
           16 C Operated roller 
           17  Lift roller 
           18  Decoupling cam rail 
           19  Rod (guided member) 
           20  Guiding member 
           20 A Upper surface (height holding means) 
           21  Friction roller 
           22  Backup roller 
           23  and  24  Coupling rod 
           23 A and  24 A Coupling roller