Abstract:
For handling elongate and flat workpieces flowing in a manufacturing line, two arrangements are disclosed, one being an arrangement including a workpiece posture changing device which changes the posture of each workpiece at the time when the workpiece is transmitted from a first conveyer to a second conveyer, and the other being an arrangement for bundling the workpiece flowing in the manufacturing line.

Description:
This application is a Divisional application of Ser. No. 09/414,167, filed Oct. 8, 1999 now U.S. Pat. No. 6,276,513. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to manufacturing lines for manufacturing heat exchangers used in automotive air conditioners, each heat exchanger comprising a plurality of parallel flat heat extending tubes arranged to constitute a rectangular mass, a plurality of outer fins alternatively arranged in the mass of the flat heat extending tubes and two header pipes connected to opposed sides of the mass. More particularly, the present invention relates to the heat exchanger manufacturing lines of a type which comprises a header pipe producing device which produces the header pipes by pressing or curling flat metal plates, a flat tube producing device which produces the flat heat exchanging tubes each including an elongate flat metal tube and an elongate inner metal fin installed in the flat tube, an outer fin producing device which produces the outer fins by corrugating an elongate metal plate, and assembling devices which produce the heat exchangers one after another by assembling the header pipes, the elongate flat tubes and the outer fins. More specifically, the present invention is concerned with workpiece handling devices arranged in the heat exchanger manufacturing line, which handle the flat heat exchanging tubes for assisting the operation of the above-mentioned producing and assembling devices. 
     2. Description of the Prior Art 
     In the heat exchanger manufacturing lines of the above-mentioned type, there are employed various handling devices for handling workpieces or flat tubes. One of the handling devices is a workpiece posture changing device which is arranged between first and second conveyers to change the posture of a workpiece, which has just released from the first conveyer, for properly putting it on the second conveyer. Another handling device is a workpiece bundling device which is arranged at a terminal position of a conveyer for bundling a certain number of the workpieces which have been conveyed thereto by the conveyer. However, some of the workpiece posture changing devices and the workpiece bundling devices hitherto proposed have failed to provide users with a satisfaction due to their insufficient handling efficiency. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a workpiece posture changing device which can exhibit a satisfied handling efficiency. 
     It is another object of the present invention to provide a workpiece bundling device which can exhibit a satisfied handling efficiency. 
     According to a first aspect of the present invention, there is provided an arrangement for handling elongate and flat workpieces flowing in a manufacturing line. The arrangement comprises a first conveyer for conveying the workpieces in such a manner that workpieces on the first conveyer are oriented transversely relative to the first conveyer; a second conveyer arranged just downstream of the first conveyer for catching and conveying the workpieces which have been just released from the first conveyer, the second conveyer having an entrance end positioned below an exit end of the first conveyer; and a workpiece posture changing device positioned just downstream of the exit end of the first conveyer and just above the entrance end of the second conveyer, the workpiece posture changing device having, at a side facing the exit end of the first conveyer, a recess which momentarily catches a leading edge of each workpiece released from the first conveyer before the workpiece falls onto the entrance end of the second conveyer. 
     According to a second aspect of the present invention, there is provided an arrangement for bundling elongate and flat workpieces flowing in a manufacturing line. The arrangement comprises two tables horizontally arranged keeping a certain clearance therebetween; a conveying device for conveying the workpieces onto the two tables to make a mass of workpieces on the two tables; a tray feeding mechanism for feeding empty trays to a position below the two tables one after another; a tray lifting mechanism positioned below the two tables, the tray lifting mechanism lifting up the empty tray through the certain clearance to permit the tray to receive therein the mass of workpieces; a tray catching mechanism for catching the tray lifted up by the tray lifting mechanism and piling up a certain number of the trays to form a mass of piled trays; and a tray mass pushing mechanism for pushing the mash of piled trays to a certain rest position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other object and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a schematically illustrated side view of a manufacturing line which employs therein a workpiece posture changing device of a first embodiment of the present invention; 
     FIG. 2 is an enlarged perspective view of the workpiece posture changing device of the first embodiment with some members associated therewith; 
     FIG. 3 is an enlarged side view of the essential portion of the workpiece posture changing device of the first embodiment; 
     FIGS. 4A and 4B are drawings showing steps for producing a flat tube, in which FIG. 4A is a perspective view of a semi-finished flat tube, and FIG. 4B is a sectional view of a finished, flat tube; 
     FIG. 5 is a plan view of a workpiece bundling device which is a second embodiment of the present invention; 
     FIG. 6 is a side view of the workpiece bundling device of the second embodiment; 
     FIG. 7 is a perspective view of the workpiece bundling device of the second embodiment with some devices removed; 
     FIG. 8 is an enlarged plan view of a tray table of a tray lifting mechanism employed in the work piece bundling device of the second embodiment; 
     FIG. 9 is a view taken from the direction if the arrow “IX” of FIG. 8; 
     FIG. 10 is a view taken from the direction of the arrow “X” of FIG. 8; 
     FIG. 11 is a plan view of the tray lifting mechanism employed in the workpiece bundling device of the second embodiment; 
     FIG. 12 is a view taken from the direction of the arrow “XII” of FIG. 11; 
     FIG. 13 is a plan view of a tray pushing mechanism employed in the workpiece bundling device of the second embodiment; 
     FIG. 14 is a view taken from the direction of the arrow “XIV” of FIG. 13; and 
     FIG. 15 is a plan view of a tray collecting structure employed in the workpiece bundling device of the second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the following, first and second embodiments  100  and  200  of the present invention will be described with reference to the accompanying drawings. 
     In the description, directional terms, such as “forward”, “backward”, “upstream”, “downstream”, “downward” and the like are used for ease of understanding the construction of the invention. Such terms are to be understood with respect to a direction in which workpieces  102  flow. 
     Referring to FIGS. 1 to  4 B, particularly FIG. 1, there is shown a workpiece posture changing device  100  of a first embodiment of the present invention, which is arranged in a manufacturing line of producing a condenser of an automotive air conditioner. 
     In FIG. 1, denoted by numeral  101  is a press machine for continuously producing flat tubes  102  used as essential elements of a core unit of the condenser. The flat tube  102  is shown in FIG.  4 . As shown in FIG. 1, the press machine  101  comprises a fixed die  101   a  and a movable die  101   b.    
     As is seen from FIG. 3, the rear end of the first conveyer  106  is equipped with another shooter  112  for shooting the flat tubes  102  toward a desired direction. The shooter  112  comprises two identical plates each having a sloped upper edge  112   a.  As shown, the sloped upper edge  112   a  has a lower portion incorporated with the work surface of the first conveyer  106 . Thus, when conveyed to the rear end of the first conveyer  106 , the flat tubes  102  are automatically put on the sloped upper edges  112   a  of the shooter  112  and thrown away toward the desired direction. 
     Behind the rear end of the first conveyer  106 , there is arranged the workpiece posture changing device  100 . As will be described in detail hereinafter, the workpiece posture changing device  100  functions to turn the posture of the flat tube  102  by about 90 degrees during the time when the flat tube  102  is transmitted from the first conveyer  106  to a second conveyer  108   
     As is seen from FIG. 2, the second conveyer  108  is a so-called screw conveyer which comprises a pair of screw rods  108  which extend in parallel with an axis of the first conveyer  106 . Each screw rod  108  has a helical groove formed thereabout. Thus, when, with the two screw rods  108  rotating in the same direction, a flat tube  102  is put into synchronous front portions of the respective grooves of the screw rods  108 , the flat tube  102  is conveyed toward the rear ends of the rods  108 . 
     As is understood from FIGS. 2 and 3, the workpiece posture changing device  100  comprises two identical catch plates  110  and  110  which are arranged above the front or entrance portions of the screw rods  108  in a manner to face the rear or exit end of the first conveyer  6 . That is, the catch plates  110  and  110  are so positioned as to catch or stop the flat tubes  102  which have been thrown away from the rear end of the first conveyer  106 . More specifically, under operation of the first convener  106 , the flat tubes  102  are thrown away one after another from the shooter  112  of the first conveyer  6  due to the inertia applied thereto. 
     For producing the flat tube  102  by the press machine  101 , the following production steps are carried out. That is, as is seen from FIGS. 1 and 4, a flat and elongate aluminum plate  103  is horizontally oriented and put between the two dies  101   a  and  101   b,  and the movable die  101   b  is moved toward the fixed die  101   a  and then moved away from the fixed die  101   a.  With this, as is seen from FIG. 4A, the plate  103  is bent at its vertically middle portion  103   b  to form a V-bent member which has a generally V-shaped cross section. The V-bent member  103  has opposed upper ends  103   a  and  103   a  each being depressed toward each other. Then, an aluminum inner fin  104  is put into the V-bent member  103 , and then the V-bent member  103  is tightly pressed by the two dies  101   a  and  101   b  with pressing forces “P” and “P” having, as is shown in FIG. 4B, the opposed upper ends  103   a  and  103   a  crimped. With this, the flat tube  102  is produced. Upon assembly of the condenser, a refrigerant flows in the flat tube  102 . It is to be noted that after completion of the above-mentioned production steps, the same steps are carried out one after another for producing other flat tubes  102 . 
     Referring back to FIG. 1, below the press machine  101 , there is arranged a shooter  105  which has a concave upper surface for smoothly receiving the flat tubes  102  produced by the press machine  101 . It is to be noted that when falling onto the concave upper surface of the shooter  105  from the press machine  101 , the flat tube  102  takes such a posture that the crimped ends  103   a  and  103   a  thereof are directed rearward as is seen from FIG.  1 . Behind the shooter  105 , there is arranged a first conveyer  106  which has a front end connected to a rear portion of the shooter  105 . Thus, after separating from the shooter  105 , each flat tube  102  is automatically put on the first conveyer  106  and conveyed toward a rear end of the conveyer  106 . During the conveying, the flat tubes  102  are transversely held on the conveyer  106  while keeping a constant pitch between every adjacent flat tubes  102 . 
     As is seen from FIG. 2, the two catch plates  110  and  110  are mounted on a fixed frame  109  while keeping therebetween a certain distance which is smaller than the length of each flat tube  102 . 
     As is seen from FIG. 3, each catch plate  110  is formed at its front edge a recess  111  whose lower edge  111   a  is convexly curved. It is to be noted that the recesses  111  of the catch plates  110  and  110  are positioned on an imaginary plane which is defined by the sloped upper edges  112   a  of the shooter  112 . 
     Between the shooter  112  and the workpiece posture changing device  100 , more specifically, between the two identical plates of the shooter  112  and the two catch plates  110  and  110  of the workpiece posture changing device  100 , there is defined a workpiece guiding space  113  by which the flat tubes  102  are appropriately guided during falling from the recesses  111  toward the second conveyer  108 . 
     In the following, operation of the workpiece posture changing device  100  of the first embodiment will be described with reference to FIG.  3 . 
     As is described hereinabove, under operation of the first conveyer  106 , the flat tubes  102  conveyed by the first conveyer  106  are thrown out from the shooter  112 . The flat tubes  102  thrown out from the shooter  112  are thus forced to collide against the catch plates  110  and  110 . That is, each flat tube  102  is forced to enter the recesses  111  of the catch plates  110  and  110  while directing the laterally middle bent portion  103   b  thereof toward the recesses  111 . When the bent portion  103   b  of the flat tube  102  collides against bottoms  111   b  of the recesses  111 , the flat tube  102  is pivoted down by its own weight and slides down along the convexly curved lower edges  111   a  of the recesses  111 , and then, the flat tube  102  is dropped down toward the second conveyer  108  while being guided by the workpiece guiding space  113 . And, finally, the flat tube  102  is put into the synchronously rotated front grooved portions of the screw rods  108 . It is now to be noted that when the flat tube  102  is received by the screw rods  108 , the same is so postured that the crimped end  103   a  thereof is directed downward. 
     As is understood from the foregoing description, the workpiece posture changing device  100  can assuredly change the posture of the flat tube  102  by about, 90 degrees during the time when the flat tube  102  is transmitted from the first conveyer  106  to the second conveyer  108 . The device  100  can be made simple in construction and compact in size. Due to provision of the grooves  111  of the catch plates  110  and  110 , the posture changing of the flat tubes  102  is much assured. That is, by the grooves  111 , the pivoting of each flat tube  101  by the own weight is smoothly achieved. Furthermore, due to provision of the workpiece guiding space  113 , the falling of the flat tubes  102  toward the second conveyer  108  is smoothly made. 
     Referring to Figs. FIGS. 5 to  15 , particularly FIGS. 5 to  7 , there is shown a workpiece bundling device  200  which is a second embodiment of the present invention. It is to be noted that the workpiece bundling device  200  is positioned just downstream of the above-mentioned workpiece posture changing device  100 . 
     As is best seen from FIG. 7, the workpiece bundling device  200  comprises a base stand  1  which is constructed of frame members. Two rectangular flat tables  2  and  2  are horizontally arranged on the base stand  1  keeping a certain distance therebetween. The tables  2  and  2  have at their rear ends respective rectangular cuts (no numeral) to which downstream ends of the above-mentioned screw rods  108  are exposed. The two screw rods  108  and  108  constitute the screw conveyer  108  (see FIG. 2) by which flat tubes  102  are conveyed to the tables  2  and  2  from the upstream end of the screw conveyer  108 . As has been mentioned in the section of the first embodiment  100 , during the conveyance of the flat tubes  102 , each flat tube  102  stands vertically having the crimped end  103   a  thereof directed downward. 
     The positional relation of the above-mentioned first conveyer  106  and the workpiece posture changing device  100  relative to the workpiece bundling device  200  is clearly seen from FIGS. 5 and 6. 
     As is seen from FIG. 5, beside the two screw rods  108  and  108 , there are arranged elongate guide plates  6  and  6  for the flat tubes  102 , each guide plate  6  extending along the screw rod  108 . However, as shown, the distance between the two guide plates  6  and  6  gradually reduces as nearing the tables  2  and  2 . With these guide plates  6  and  6 , the flat tubes  102  are appropriately guided when conveyed by the screw conveyer  108  toward the tables  2  and  2 . More specifically, the two guide plates  6  and  6  are so arranged as to put the flat tubes  102  on the tables  2  and  2  in such a manner that the center of each flat tube  102  is placed at a center between the tables  2  and  2 . 
     Referring back to FIG. 7, the tables  2  and  2  are equipped at their downstream ends with respective stoppers  7 . With these stoppers  7  and  7 , the tables  2  and  2  can put or collect thereon a certain number (for example, one hundred) of flat tubes  102 . 
     In order to allow the flat tubes  102  to stand vertically on the tables  2  and  2 , a holding mechanism is employed. 
     The holding mechanism comprises two holding arms  8  and  8  which are moved fore-and-aft above the tables  2  and  2 . 
     As is seen from FIGS. 8 and 9, for moving the two holding arms  8  and  8 , two power cylinders  9  and  9  are provided, each having a piston connected to the corresponding holding arm  8 . As is seen from FIGS. 8 to  10 , the movement of each holding arm  8  is guided by a guide mechanism  10  which comprises a guide rail  10   a  which extends along an inner edge of the corresponding table  2  and a slider piece  10   b  which is connected to the holding arm  8 . The slider pieces  10   b  are slidably engaged with the guide rails  10   a  and  10   a  and connected to leading ends of piston stems of the power cylinders  9  and  9 . 
     The forward movement of the holding arms  8  and  8  is synchronized with the forward movement of the flat tubes  102  conveyed by the screw conveyer  108 . That is, each time a flat tube  102  is released from the screw conveyer  108 , the holding arms  8  and  8  advance a little to hold the released flat tube  102 . With increase of number of the flat tubes  102  released from the screw conveyer  108 , the holding arms  8  and  8  move toward the stoppers  7  and  7  to hold all of these released flat tubes  102  on the tables  2  and  2 . When the holding arms  8  and  8  reach the stoppers  7  and  7 , that is, when the flat tubes  102  accumulated on the tables  2  and  2  show a certain number (for example, one hundred), all of these flat tubes  102  are lifted up by an after-described tray lifting mechanism  13  thereby emptying the tables  2  and  2 . Upon this, the holding arms  8  and  8  are returned back to their original or stand-by positions for carrying out a subsequent holding operation. 
     As is best seen from FIGS. 8 and 9, below and between the tables  2  and  2 , there is arranged the tray lifting mechanism  13  which lifts up a rectangular tray  11  for receiving the above-mentioned all of the flat tubes  102  into the tray  11 . 
     As is seen from FIG. 7, the tray  11  comprises a rectangular base portion, opposed side walls  12  and  12  and flanges  12   a  and  12   a  formed on the side walls  12  and  12 . 
     Referring back to FIGS. 8 and 9, the tray lifting mechanism  13  comprises a power cylinder  15  and a rectangular tray table  14  vertically driven by the power cylinder  15 . That is, the tray table  14  is mounted on a leading end of a piston stem of the power cylinder  15 . The tray table  14  is sized to stably hold thereon the tray  11 . 
     As is seen from FIGS. 9 and 10, for smoothing the vertical movement of the table  14 , there is employed a guide mechanism. The guide mechanism comprises two guide rods  16  and  16  fixed to the tray table  14  and two rod holders  17  fixed to the power cylinder  15 . Each guide rod  16  is slidably engaged with the corresponding rod holder  17 . 
     As is seen from FIGS. 8,  9  and  11 , on both sides of the tray table  14 , there are arranged two groups of rollers  18  and  18  respectively. More specifically, the rollers  18  of each group are aligned on an imaginary line which is in parallel with the axis of the screw conveyer  108 . These rollers  18  and  18  are used for facilitating movement of the tray  11  toward an after-described tray collecting structure  30  (see FIG.  14 ). 
     As is seen from FIGS. 9,  11  and  12 , near the downstream ones of the two groups of rollers  18  and  18 , there is arranged a tray positioning mechanism which comprises two power cylinders  20  and  20  which are fixed to the tray table  14  and stopper pins  19  which are vertically driven by the power cylinders  20  and  20 . That is, when the power cylinders  20  and  20  are energized, the stopper pins  19  and  19  are projected upward to serve as a stopper means for the tray  11 . The function of the stopper pins  19  and  19  will be well understood from FIG.  12 . That is, while the tray lifting mechanism  13  is operating to put toe flat tubes  102  onto the tray  11 , the stopper pins  19  and  19  are kept projected for suppressing movement of the tray  11 . While, when the tray  11  is about to be moved to the tray collecting structure  30 , the stopper pins  19  and  19  are drawn into the power cylinders  20  and  20  to permit the movement of the tray  11  toward the position. 
     As is seen from FIGS. 7,  13  and  14 , above the tables  2  and  2 , there are arranged two, that is, outside an inside frames  21 A and  21 B which extend in a direction perpendicular to the axis of the screw conveyer  108 . Mounted on the two frames  21 A and  21 B is a tray catching mechanism which functions to catch the tray  11  which has been lifted up by the tray lifting mechanism  13 . 
     As is best seen from FIG. 13, the tray catching mechanism comprises two pairs of brackets  23  which are respectively secured to the frames  21 A and  21 B. The paired brackets  23  have respective pivot arms  22  pivotally connected thereto. Each pivot arm  22  is pivotal between a horizontal position wherein, as is illustrated by a solid line in FIG. 14, the arm  22  is directed toward the opposite frame  21  and a vertical position wherein the arm  22  is directed upward. Although not shown in the drawings, a biasing spring is applied to each pivot arm  22  to bias the same toward the horizontal position. Thus, usually the pivot arms  22  assume the horizontal positions due to the work of the biasing springs. While, when, during upward movement of the tray  11  by the tray lifting mechanism  13 , the tray  11  collides against lower surfaces of the pivot arms  22 , these pivot arms  22  are forced to pivot upward against the force of the biasing springs and finally permit passing of the tray  11  therethrough as will be understood from the positions of the pivot arms  22  illustrated by solid lines in FIG.  14 . Once this passing is completed, the pivot arms  22  are turned back to the horizontal positions. Thus, when thereafter the tray lifting mechanism  13  lowers the trays  11 , the tray  11  becomes supported at its flanges  12   a  by the pivot arms  22 , as is seen from FIG.  14 . 
     Referring back to FIG. 7, on the inside frame  21 B, there is mounted a tray mass pushing mechanism which functions to push a mass of the trays  11 , which is kept supported by the pivot arms  22 , toward the tray collecting structure  30  (see FIG. 14) which is positioned beside the outside frame  21 . 
     As is seen from FIGS. 7 and 14, the tray mass pushing mechanism comprises a back plate  26  secured to the inside frame  21 B, a power cylinder  25  secured to the back plate  26  and a pushing plate  24  driven by a piston of the power cylinder  25 . That is, upon energization of the power cylinder  25 , the pushing plate  24  is moved toward the outside frame  21 A to push the tray  11 . 
     As is seen from FIGS. 7,  13  and  14 , for smoothing the movement of the pushing plate  24 , a guide mechanism is employed which comprises a pair of guide rods  27  secured to the pushing plate  24  and rod holders  28  secured to the power cylinder  25 . The guide rods  27  are slidably held by the rod holders  28 . 
     As is seen from FIGS. 7 and 14, the back plate  26  of the tray mass pushing mechanism has a lower portion sandwiched between the inside frame  21 B and the inside p aired brackets  23  of the tray catching mechanism. 
     As is seen from FIG. 7, the back plate  26  is provided at lateral sides thereof with holding pieces  29  and  29  which function to hold a back side of the mass of the flat tubes  102  in the lifted up tray  11 . 
     As will be seen from FIG. 14, in operation of the workpiece bundling device  200 , a plurality of trays  11  are piled on the pivot arms  22  due to subsequent insertion of a new tray  11  into a space below the mass of the piled trays  11 . When the number of the piled trays  11  comes to a certain value, and thus, when, due to operation of the tray lifting mechanism  13 , the mass of the piled trays  11  comes up to show a certain height as is shown in FIG. 14, the pushing plate  24  of the tray mass pushing mechanism pushes the mass toward the tray collecting structure  30 . 
     As is seen from FIGS. 5,  14  and  15 , the tray collecting structure  30  comprises two horizontal frames  30 A and  30 B. On the frames  30 A and  30 B, there is mounted a base structure  30 C which carries thereon a roller conveyer  31  and a tray stopper  33 . Extending along the roller conveyer  31  are guide rails  32 A and  32 B for guiding the movement of the mass of the piled trays  11  to a right position. When coming to the right position, the mass of the piled trays  11  abuts against the tray stepper  33 . 
     Referring back to FIG. 7, on the other side of the base stand  1 , there are arranged two tray feeding mechanisms  34 A and  34 B and a tray moving mechanism  39 . Each tray feeding mechanism  34 A or  34 B functions to feed the tray lifting mechanism  13  with empty trays one after another. That is, when one tray feeding mechanism  34 A or  34 B exhausts the empty trays  11  piled thereon, the other tray feeding mechanism  34 B or  34 A starts the tray feeding. The tray moving mechanism  39  functions to move one empty tray  11  to the above-mentioned tray lifting mechanism  13 . 
     Since the two tray feeding mechanisms  34 A and  34 B are the same in construction, only the mechanism  34 A will be described for facilitation of the description. 
     The tray feeding mechanism  34 A comprises a tray stand  35  which has two vertically extending rails  36  secured thereto, and two tray holders  37 A and  37 B which are arranged near a lower part of the tray stand  35 . The two tray holders  37 A and  37 B function to support the lowermost one of the riled empty trays  11 . More specifically, the tray holders  37 A and  37 B support the flanges  12   a  of the lowermost tray  11 . 
     The insider and outside tray holders  37 A and  37 B are horizontally driven by power cylinder mechanisms  38 A. That is, due to function of the power cylinder mechanism  38 A, the inside and outside tray holders  37 A and  37 B can move toward and away from each other. The movement of the tray holders  37 A and  37 B is smoothed by a guide mechanism which comprises a guide rod  38   a  and a slide guide  38   b.  These two members  38   a  and  38   b  are slidably engaged. 
     The outside tray holder  37 B is vertically driven by another power cylinder mechanism  38 B. That is, due to incorporated operation of the two power cylinder mechanisms  38 A and  38 B, the tray feeding mechanism  34 A or  34 B establishes a tray holding operation. 
     Below the inside and outside tray holders  37 A and  37 B, there extend two guide rails  40  each extending to the above-mentioned tray lifting mechanism  13 . 
     When, with the empty trays  11  piled on the tray holders  37 A and  37 B, the outside tray holder  37 B is moved away from the inside tray holder  37 A by a certain distance by the power cylinder mechanism  38 A, the lowermost one of the mass of the piled trays  11  is released from the tray holders  37 A and  37 B and thus dropped onto the guide rails  40 . 
     Each guide rail  40  is provided with guide plates  41  by which the piled empty trays  11  are snugly and neatly put on the tray holders  37 A and  37 B. 
     The tray moving mechanism  39  functions to move the released lowermost tray  11  on and along the guide rails  40  to the tray lifting mechanism  13 . During this movement, the tray lifting mechanism  13  keeps the tray table  14  thereof at the lower position to permit putting of the tray  11  onto the tray table  14 . The tray moving mechanism  39  comprises generally a guide rail  43  which extends along the guide rails  40  and a moving plate  42  which moves along the guide rail  43 . Although not shown, the moving plate  42  is driven by a power cylinder mechanism. As is understood from FIG. 10, when, due to operation of the power cylinder mechanism, the moving plate  42  moves the released empty tray  11  to the tray table of the tray lifting mechanism  13 , the tray  11  abuts against a stopper  44  which is fixed to the tray table  14 . 
     In the following, operation of the workpiece bundling device  200  will be described with reference to the drawings, particularly FIG.  7 . 
     Each time a flat tube  102  is released from the screw conveyer  108 , the holding arms  8  and  8  advance a little to hole the released flat tube  102 . With increase of number of the flat tubes  102  released from the screw conveyer  108 , the holding arms  8  and  8  move toward the stoppers  7  and  7  to hold all of these released flat tubes  102  on the tables  2  and  2 . It is to be noted that during this flat tube feeding operation, the tray table  14  of the tray lifting mechanism  13  assumes its lower position, that is, the position below the tables  2  and  2 . 
     During the flat tube feeding operation of the screw conveyer  108 , the tray holders  37 A and  37 B of the tray feeding mechanism  34 A or  34 B are moved away from each other to drop the lowermost tray  11  (or first empty tray  11 ) of the mass of the piled empty trays  11  onto the guide rails  40  and due to operation of the tray moving mechanism  39 , the first empty tray  11  is shifted to the position just above the tray table  14  of the tray lifting mechanism  13 . 
     When the flat tubes  102  accumulated on the tables  2  and  2  show a certain number (for example, one hundred), the tray lifting mechanism  13  is operated to lift up the tray table  14  and thus put the first empty tray  11  on the tray table  14 . Due to the lifting of the first tray  11  between the tables  2  and  2 , all of the accumulated flat tubes  102  on the tables  2  and  2  are received by the tray  11 . 
     As is seen from FIG. 14, further lifting of the first tray  11  by the tray lifting mechanism  13  causes the flanges  12   a  of the first tray  11  to pass up through the pivot arms  22  of the tray catching mechanism while pivoting the pivot arms  22  upward. Upon completion of passing of the flanges  12   a  through the pivot arms  22 , the pivot arms  22  are pivoted down to assume the horizontal position. Thereafter, the tray lifting mechanism  13  is operated to lower the tray table  14 . With this, the first tray  11  having all of the flat tubes  102  received therein becomes supported at its flanges  12   a  by the horizontal pivot arms  22 . 
     As is understood from FIG. 7, when the tray table  14  of the tray lifting mechanism  13  is lowered to a certain lower position, the holding arms  8  and  8  are instantly returned back to the original position or stand-by position for dealing with a subsequent flat tube accumulation operation. Of course, during the subsequent flat tube accumulating operation, the tray moving mechanism  39  brings a second empty tray  11  to the position just above the lowered tray table  14  of the tray lifting mechanism  13 . Thereafter, the second empty tray  11  is lifted up by the tray lifting mechanism  13  in the same manner as that mentioned hereinabove and thus, the second tray  11  receives therein another mass of the flat tubes  102 . The second tray  11  is finally supported at its flanges  12   a  by the pivot arms  22  supporting thereon the first tray  11 . 
     When the above-mentioned operation is repeated for certain times, a plurality of trays  11  are piled on the pivot arms  22  of the tray catching mechanism. 
     When, as is seen from FIG. 14, the number of the piled trays  11  shows a certain value, and thus, when, due to operation of the tray lifting mechanism  13 , the mass of the piled trays  11  is brought to a certain height, the pushing plate  24  of the tray mass pushing mechanism pushes the mass of the piled trays  11  to the tray collecting structure  30 . The movement of the mass toward the tray collecting structure  30  is smoothly made by the provision of the two groups of rollers  18  and  18  on the ray table  14 . 
     As is described hereinabove, in the workpiece bundling device of the second embodiment  200 , a certain number of flat tubes  102  can be put onto the tables  2  and  2  while standing vertically. Thereafter, the mass of the flat tubes  102  is received by the tray  11  lifted up by the tray lifting mechanism. Then, the tray filled with the flat tubes  102  is held by the pivot arms  22  of the tray catching mechanism. By repeating the above-mentioned operation, a certain number of trays  11  are piled on the pivot arms  22  of the tray catching mechanism. Upon this, the tray mass pushing mechanism pushes the mass of the piled trays  11  to the tray collecting structure  30 . 
     During this, the tray feeding mechanism feeds empty trays to the tray lifting mechanism one after another. 
     Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings.