Abstract:
An overhead traveling carrier system carries a package along a rail supported by a roof, and stops a vehicle at a target position; when the vehicle of the overhead traveling carrier system enters an area around the target position, the overhead traveling carrier system stops the vehicle, and changes the relative position between the vehicle and a handling unit mounted on the vehicle during the downward motion of the handling unit toward the destination, thereby speedily aligning the package with the destination.

Description:
FIELD OF THE INVENTION 
     This invention relates to an overhead traveling carrying technology and, more particularly, to an overhead traveling carrier system and a method for controlling thereof. 
     DESCRIPTION OF THE RELATED ART 
     The overhead traveling carrier system is, by way of example, installed in a manufacturing facility. FIGS. 1 and 2 illustrate a typical example of the overhead traveling carrier system. The prior art overhead traveling carrier system comprises a rail 1a attached to a roof (not shown), a vehicle 1b suspended from the rail 1a by means of wheels 1c and a handling mechanism 1d suspended from the vehicle 1b by means of wires 1e. The rail 1a passes over several destinations where packages are to be loaded and unloaded, and the vehicle 1b moves the handling mechanism 1d to the destinations. The handling mechanism 1d loads and unloads the packages at the destinations. 
     The vehicle 1b further includes a linear induction motor unit (not shown) and a winding mechanism 1f, and the linear induction motor unit drives the wheels 1c for rotation, and the wheels 1c roll along the rail 1a. The winding mechanism 1f winds up the wires, and releases them therefrom. 
     When the wires 1e are wound on the winding mechanism 1f, the load handling mechanism 1d is lifted from a floor 2, and stays at a home position close to the vehicle. The vehicle 1b moves the handling mechanism 1d to the destinations together with a package 3. 
     The handling mechanism 1d includes a table 1g, fixed to the wires 1e and an arm 1h for retaining the package 3. The table 1g supports the arm 1h and the package 3, and is moved between the home position and a working position close to the floor 2. 
     When the vehicle 1b releases the wires 1e from the winding mechanism 1f, the table 1d is downwardly moved from the home position toward the working position, and stays around the floor 2. Then, the arm 1h loads and uploads the package. 
     Upon completion of the loading work or the unloading work, the vehicle 1b winds up the wires 1e, and the handling mechanism 1d returns to the home position. Then, the vehicle 1b energizes the linear induction motor unit, and the wheels 1c rolls along the rail 1a toward the next destination. 
     When the vehicle 1b arrives at the destination 4 (see FIG. 1), the vehicle 1b unwinds the wires 1e from the winding mechanism 1f, and the handling mechanism 1d reaches the working position close to the floor 2 (see FIG. 2). Then, the arm 1h unloads the package 3, and places it on the destination 4. 
     Though not shown in FIGS. 1 and 2, a controller is provided for the prior art overhead traveling carrier system, and controls the prior art overhead traveling carrier system at the destination 4 as follows. 
     FIG. 3 illustrates the controlling sequence executed by the controller. When the vehicle 1b arrives around the destination as by step SP1, the controller instructs the vehicle 1b to stop the wheels 1c as by step SP2, and checks the current position to see whether or not the vehicle stops at the target point over the destination 4. If the current position is deviated from the target position, the controller instructs the vehicle 1b to correct the current position as by step SP3. 
     When the current position is matched with the target position, the controller receives a report representative of the completion of the correction as by step SP4, and instructs the vehicle 1b to downwardly move the handling mechanism 1d as by step SP5. 
     The handling mechanism 1d is downwardly moved together with the package 3, and places the package at the destination 4. The handling mechanism 1d releases the package 3 as by step SP6. Then, the controller instructs the vehicle 1b to wind the wires 1e, and the handling mechanism 1d is lifted toward the vehicle 1b. When the handling mechanism 1d reaches close to the vehicle, the controller instructs the vehicle 1b to return to the next position. 
     However, a problem is encountered in that the prior art overhead traveling carrier system can not speedily convey the package 3. 
     SUMMARY OF THE INVENTION 
     It is therefore an important object of the present invention to provide an overhead traveling carrier system, which conveys a load speedily. 
     It is also an important object of the present invention to provide a method for controlling the overhead traveling carrier system to speedily convey a load. 
     The present inventor contemplated the problem, and noticed that the correction of position consumed a long time. This is because of the fact that total weight of the vehicle 1b, the handling mechanism 1d and the package 3 was so heavy. Another reason was that the wires 1e were liable to swing the handling mechanism during the unwinding motion. 
     To accomplish the object, the present inventor proposes to match a current position with a target position through a relative motion between a vehicle and a handling mechanism. 
     In accordance with one aspect of the present invention, there is provided an overhead traveling carrier system for conveying an object between destinations, comprising a path extending over the destinations; a vehicle moving along the path; a handling unit supported by the vehicle, and having a retainer movable between a working position closer to the destinations for loading and unloading the object and a home position closer to the vehicle for carrying the object between the destinations; a primary aligner monitoring a first relative relation between a current position of the vehicle and an actual position of each of the destinations so as to stop the vehicle around the actual position; and a secondary aligner monitoring a second relative relation between a current position of the handling unit and the actual position so as to align the handling unit with each of the destinations after the primary aligner stops the vehicle around the actual position. 
     In accordance with another aspect of the present invention, there is provided a method of controlling an overhead traveling carrier system, comprising the steps of: checking a current position of a vehicle to see whether or not the vehicle enters into an area around a target position; stopping the vehicle when the vehicle enters into the area; changing a relative position between the vehicle and a handling unit movably supported by the vehicle so as to align the handling unit with the target position while the handling unit is being released from a home position closer to the vehicle toward a working position closer to a destination at the target position; and loading or unloading an object at the destination. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the overhead traveling carrier system and the method will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a schematic view showing the prior art overhead traveling carrier system at the home position; 
     FIG. 2 is a schematic view showing the prior art overhead traveling carrier system at the working position; 
     FIG. 3 is a flowchart executed by the controller during the unloading work; 
     FIG. 4 is a schematic view showing an overhead traveling carrier system at a home position; 
     FIG. 5 is a schematic view showing the overhead traveling carrier system at a working position; 
     FIG. 6 is a side view showing a position aligner incorporated in the overhead traveling carrier system; 
     FIG. 7 is a bottom view showing the aligner; 
     FIGS. 8A and 8B are flowcharts showing a program sequence executed by a controller incorporated in the overhead traveling carrier system; 
     FIG. 9 is a side view showing an aligner incorporated in another overhead traveling carrier system according to the present invention; and 
     FIG. 10 is a bottom view showing the aligner. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 4 and 5 of the drawings, an overhead traveling carrier system embodying the present invention largely comprises a rail 10a attached to a roof of a manufacturing facility, a vehicle 10b movable along the rail 10a in a first direction, a handling mechanism 10c movable in a direction parallel to the first direction for loading and unloading a package 12 and a controller 10d for controlling the vehicle 10b and the handling mechanism 10c. The package 12 is loaded by the loading mechanism at a working position (see FIG. 5), and the vehicle 10b conveys the handling mechanism 10c together with the package 12 at a home position (see FIG. 4) from the loading area to an unloading area. 
     The vehicle 10b includes a frame 10ea, wheels 10f suspending the frame 10ea from the rail 10a and an electric motor unit 10g driving the wheels 10f. When the controller 10d instructs the vehicle 10b to energize the electric motor 10g, the wheels 10f are driven for rotation by the electric motor unit 10g, and roll along the rail 10a in either direction depending upon the instruction of the controller 10d as indicated by arrow AR1. 
     The handling mechanism 10c includes a frame 10eb, an electric motor unit 10h accommodated in the frame 10eb, a multiple-link lifter 10i attached to the lower surface of the frame 10eb and two pairs of sliders 10ja/10jb connected between the electric motor unit 10b and the multiple-link lifter 10i. The multiple-link lifter 10i is implemented by a plurality of pairs of links 10k/10m. The links 10k crosses the associated links 10m, and are rotatably connected thereto by means of pins 10n at intermediate points thereof, respectively. The pair of links 10k/10m closest to the frame 10eb is rotatably connected to the pair of sliders 10ja at upper ends thereof by means of pins 10o, and each pair of links 10k/10m is rotatably connected to another pair of or the other pairs of links 10k/10m at upper/lower ends thereof by means of pins 10p. 
     The pair of links 10k/10m farthest from the frame 10e is rotatably connected to the other pair of sliders 10jb by means of pins 10q. 
     The electric motor unit 10h is bi-directionally rotated so that the sliders 10ja are approached to and spaced from each other. When the sliders 10ja are spaced from each other, the sliders 10ja make the angle AG between the links 10k and 10m large, and the pairs of links 10k/10m minimize the length as shown in FIG. 4. On the other hand, when the sliders 10ja are close to each other, the angle AG is decreased, and the length of the pairs of links 10k/10m is maximized as shown in FIG. 5. The pairs of links 10k/10m transfer the angle AG between the pair of sliders 10ja and the other pair of sliders 10jb, and positions the pair of sliders 10jb at the corresponding position of the pair of sliders 10ja. 
     The handling mechanism 10c further includes a table 10r supporting the sliders 10jb, an arm 10s supported by the table 10r for retaining the package 12. When the pairs of links 10k/10m minimize the length, the handling mechanism 10c enters into the home position, and the table 10r and the arm 10s are lifted to the closest position to the vehicle 10b. On the other hand, when the pairs of links 10k/10m maximizes the length, the handling mechanism 10c reaches the working position, and the package 12 is loaded or unloaded by means of the arm 10s. 
     Turning to FIGS. 6 and 7 of the drawings, the overhead traveling carrier system further comprises a first aligner 10t for roughly aligning the vehicle 1b in a first direction with the target position of a destination 13 on a floor 14 and a second aligner 10u for precisely aligning the arm 10s in a direction parallel to the first direction and, accordingly, the package 12 with the position of the destination. 
     The first aligner 10t includes a non-contact sensor 10ta fixed to a side surface of the rail 10a and a reference mark 10tb attached to the frame 10ea. The non-contact sensor 10ta monitors a trajectory of the vehicle 10b to see whether or not the reference mark 10tb arrives at a predetermined area in front of the non-contact sensor 10ta. The predetermined area is defined in the vicinity of a target position over the destination 13. When the reference mark 10tb enters into the predetermined area, the non-contact sensor 10ta changes the potential level of a detecting signal DT1 supplied to the controller 10d, and the controller 10d acknowledges the entry into the predetermined area. When the vehicle 10b enters into the predetermined area, the controller 10d instructs the electric motor 10g to stop the wheels 10f. Thus, the first aligner 10t and the controller 10d as a whole constitute a primary aligner. 
     The second aligner includes a linear motion mechanism 10ua connected between the frames 10ea and 10eb, a non-contact sensor 10ub stationary with respect to the frame 10eb and a reference mark 10uc stationary with respect to the frame 10ea. The non-contact sensor 10ub monitors the reference mark 10uc to produce a detecting signal DT2 representative of the distance between the non-contact sensor 10ub and the reference mark 10uc. Upon entry into the predetermined area, the controller 10d calculates a correction for the precise alignment between the current position of the handling mechanism 10c and the target position, and instructs the linear motion mechanism 10ua to move the handling mechanism 10c with respect to the vehicle 10b by the given correction. When the controller 10d acknowledges that the handling mechanism 10c is moved by the correction through the detecting signal DT2, the controller 10d instructs the linear motion mechanism 10ua to stop there. 
     The linear motion mechanism 10ua includes a first bracket 10ud fixed to the frame 10ea, a motor mount 10ue fixed to the frame 10eb, an electric motor unit 10uf fixed to the motor mount 10ue, a second bracket 10ug fixed to the frame 10eb, a ball thread 10uh snugly received in a hole formed in the first bracket 10ud and a threaded rod 10ui engaged with the ball thread 10uh. The threaded rod 10ui is connected at one end thereof to the rotor of the electric motor unit 10ua, and the other end portion of the threaded rod 10ui is rotatably supported by the second bracket 10ug. The non-contact sensor 10ub is supported by the second bracket 10ug, and the reference mark 10uc is fixed to the first bracket 10ud. 
     The linear motion mechanism 10ua further includes rollers rotatably supported by the frame 10eb at the four corners and two rails 10uk attached to the bottom surface of the frame 10ea in parallel to each other. The rollers 10uj are engaged with the rails 10uk, and roll along the rails 10uk. As a result, the frame 10eb is bi-directionally moved with respect to the frame 10ea. 
     When the electric motor unit 10uf rotates the threaded rod 10ui, the ball thread 10uh converts the rotation of the threaded rod 10ui to a thrust, and the thrust moves the handling mechanism 10c in one direction. On the other hand, when the electric motor unit 10uf rotates the threaded rod 10ui in the opposite direction, the threaded rod 10ui and the ball thread move the handling mechanism 10c in the opposite direction. Thus, the second aligner 10u and the controller 10d as a whole constitute a secondary aligner. 
     Description is made on the controlling sequence with reference to FIGS. 8A and 8B. Assuming now that the vehicle 10b conveys the package 12 toward the destination 13, the controller 10d periodically checks the detecting signal DT1 to see whether or not the vehicle enters the predetermined area around the target position. When the non-contact sensor 10ta changes the potential level of the detecting signal DT1, the controller 10d acknowledges the entry into the predetermined area as by step SP10, and instructs the electric motor unit 10g to stop the wheels 10f as by step SP11. 
     Subsequently, the controller 10d instructs the electric motor 10h to project the multiple-link mechanism 10i as by step SP12, and instructs the second aligner 10u for a precise alignment as by step SP13. Thus, the handling mechanism 10c is precisely aligned with the target position during the projection of the multiple-link mechanism 10i. 
     The controlling sequence for the precise alignment is illustrated in FIG. 8B. When the vehicle 10b enters into the predetermined area, the controller 10d instructs the electric motor unit 10g to stop the wheels 10f as by step SP131, and reads the potential value of the detecting signal DT1 as by step SP132. The controller 10d calculates a correction for the precise alignment between the handling mechanism 10I and the destination 13 as by step SP133. 
     Subsequently, the controller 10d reads the detecting signal DT2 to see how far the non-contact sensor 10ub is spaced from the reference mark 10uc as by step SP134. The controller 10d determines the distance over which the handling mechanism 10c has to be moved. 
     The controller 10d instructs the electric motor unit 10uf to move the handling mechanism by the distance as by step SP135. The controller 10d periodically checks the detecting signal DT2 to see whether or not the handling mechanism is moved over the distance as by step SP136. While the answer at step SP136 is given negative, the controller 10d returns to step SP135, and reiterates the loop consisting of steps SP135 and 136 until the answer at step SP136 is changed to affirmative. 
     When the answer at step SP136 is given affirmative, the controller 10d instructs the electric motor unit 10uf to stop the threaded rod 10ui as by step SP137, and the handling mechanism 10c is precisely aligned to the target position. 
     Turning back to FIG. 8A, when the multiple-link mechanism 10i maximizes the length thereof, the arm 10s reaches the destination 13, and the arm 10s unloads the package 12 as by step SP14. The controller 10d instructs the electric motor unit 10b to lift up the table 10r and the arm 10s as by step SP15. When the handling mechanism 10c returns to the home position, the controller 10d instructs the electric motor unit 10g to rotate the wheels 10f as by step SP16, and the vehicle 10b is moved toward the next destination. 
     As will be appreciated from the foregoing description, only the handling mechanism 10c is regulated to the target position, and the electric motor unit 10uf speedily moves the handling mechanism 10c to the target position. Moreover, the alignment is carried out during the projection of the multiple-link mechanism 10i, and the parallel works shrink the time consumed in the unloading operation. Thus, the overhead traveling carrier system according to the present invention speedily conveys the package to the destination. 
     Second Embodiment 
     Turning to FIGS. 9 and 10 of the drawings, a second aligner 21 incorporated in another overhead traveling carrier system embodying the present invention is supported by a vehicle. The overhead traveling carrier system implementing the second embodiment is similar to the first embodiment except for a guide mechanism 21a of the second aligner 21. For this reason, other components members and units are labeled with the same references designating corresponding members and units of the first embodiment without detailed description. 
     The guide mechanism 21a includes wheels 21b rotatably supported by the frame 10ea and guide rails 21c attached to both side surfaces of the frame 10eb. The guide rails 21c allows the wheels 21b to roll therealong, and the handling mechanism 10c is bi-directionally moved with respect to the vehicle 10b. 
     The second embodiment achieves all the advantages of the first embodiment.