Abstract:
A transfer vehicle includes a lateral pair of extendable and retractable arms, openable and closable hooks at front and rear ends of the arms, an arm opening and closing mechanism configured to change spacing between the arms, and a controller configured and programmed to control the arms and the arm opening and closing mechanism as well as the hooks. During article pickup, the controller pulls in an article onto the transfer vehicle by causing the arms to protrude to a position beyond the article in a state in which the hooks at a distal end in a pickup direction as viewed from the transfer vehicle are opened, thereafter closing the hooks to clamp the article, opening the arms after the clamping to provide a gap between the article and at least one of the arms, and retracting the arms in a state in which the hooks are closed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to transfer vehicles, and particularly to a transfer vehicle configured to transfer an article to and from racks without the article getting caught on the arms of the transfer vehicle. 
         [0003]    2. Description of the Related Art 
         [0004]    JP H11-278607A discloses a transfer vehicle including a lateral pair of arms and configured to transfer an article to and from racks by causing hooks at front and rear ends of the arms to abut the article. JP H11-278607A also discloses adjusting the spacing between the arms by moving the arms along the running direction of the transfer vehicle. However, the inventors of the present application discovered that clamping an article with arms to position the article may cause the article to get caught on the arms, resulting in damage to the article. However, if a gap is provided between the article and the arms to avoid this problem, the position to which the article is transferred becomes imprecise. Therefore, there is a need for a technique for transferring an article to a predetermined position without the article getting caught on the arms. 
       SUMMARY OF THE INVENTION 
       [0005]    Preferred embodiments of the present invention provide a transfer vehicle that pulls an article onto the transfer vehicle without the article getting caught on arms and while positioning the article. 
         [0006]    Preferred embodiments of the present invention also provide a transfer vehicle that prevents an article from being displaced on the transfer vehicle or from protruding from the transfer vehicle. 
         [0007]    Preferred embodiments of the present invention provide a transfer vehicle that drops an article off to a precise position without the article getting caught on the arms. 
         [0008]    According to a preferred embodiment of the present invention, a transfer vehicle includes a lateral pair of extendable and retractable arms, the arms each including openable and closable hooks at front and rear ends of the arms, an arm opening and closing mechanism configured to change spacing between the arms, and a controller configured and programmed to control the arms, the arm opening and closing mechanism and the hooks, the controller and programmed being configured to, during article pickup, control hooks at a distal end along a pickup direction as viewed from the transfer vehicle in a state in which the hooks are opened, while controlling the arms such that the arms are advanced so as to protrude from the transfer vehicle to a position where the hooks at the distal end pass the article, control the arm opening and closing mechanism by closing the advanced arms so as to clamp the article and opening the arms after the clamping, such that a gap is provided between the article and at least one of the arms, and control the hooks at the distal ends to be in a closed state in order to pull the article onto the transfer vehicle, while controlling the arms such that the arms are retracted. 
         [0009]    The hooks at the distal end may be closed between the clamping of the article and the start of pulling the article. Both of the arms may be movable along the running direction of the transfer vehicle, or only one of the arms may be movable. 
         [0010]    According to a preferred embodiment of the present invention, the article is clamped by the arms before the article is pulled in, and therefore the article is positioned relative to the arms. From this state, the arms are opened to cause the hooks at the distal end to abut the arms, thus pulling the article. Accordingly, the article does not get caught on the arms, or in other words, the arms do not damage the article by strongly hitting the article. 
         [0011]    Preferably, the controller is configured and programmed to control the arm opening and closing mechanism such that the article is clamped by the arms while the transfer vehicle is running. 
         [0012]    This makes it possible to significantly reduce and prevent the displacement, vibration and the like of the article during running. 
         [0013]    Also preferably, the controller is configured and programmed to control the hooks at the front and rear ends such that the hooks are closed while the transfer vehicle is running. This makes it possible to prevent the article from protruding from the transfer vehicle during running, and particularly to prevent falling off of the article. Although the operation of closing the hooks is performed under control of the controller, the hooks may alternatively be closed automatically upon completion of retraction of the arms, without an instruction from the controller. 
         [0014]    Particularly preferably, the controller is configured to, during article drop off, control the arm opening and closing mechanism to provide a gap between at least one of the arms and the article, control the hooks at a proximal end along a drop off direction as viewed from the transfer vehicle in a state in which the hooks are closed, and control the arms such that the arms are advanced so as to protrude from the transfer vehicle. This prevents the article from getting caught on the arms during article drop off. Note that clamping the article by the arms during running allows the article to be pre-positioned relative to the transfer vehicle, so that the article may be dropped off at the target position of the racks even if a gap is provided between the article and the arms during article drop off. Even if the article is not clamped during running, temporarily clamping the article at the time of pulling the article onto the transfer vehicle allows the article to be pre-positioned relative to the transfer vehicle. Therefore, in either case, the article may be dropped off at a precise position. 
         [0015]    Another preferred embodiment of the present invention provides a transfer method for transferring an article using a transfer vehicle including openable and closable hooks at front and rear ends thereof, and also including a lateral pair of extendable and retractable arms and a controller, the method including the steps of advancing, during article pickup, the arms so as to protrude from the transfer vehicle in a state in which the hooks at a distal end along a pickup direction as viewed from the transfer vehicle, to a position at which the hooks at the distal end pass the article; subsequently closing the arms to clamp the article; and, after the clamping, pulling the article onto the transfer vehicle by opening the arms to provide a gap between the article and at least one of the arms, and further retracting the arms in a state in which the hooks at the distal end are closed, wherein the steps are performed under control of a controller. 
         [0016]    Preferably, during article drop off, a step of advancing the arms so as to protrude from the transfer vehicle in a state where a gap is provided between at least one of the arms and where the article and the hooks at a proximal end along a drop off direction as viewed from the transfer vehicle are closed is performed under control of the controller. 
         [0017]    The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a plan view showing a transfer vehicle and right and left racks according to a preferred embodiment of the present invention. 
           [0019]      FIG. 2  is a block diagram of a controller and a motor of the transfer vehicle and a warehouse controller. 
           [0020]      FIG. 3  is a flowchart illustrating an algorithm used for performing article pickup according to a preferred embodiment of the present invention. 
           [0021]      FIG. 4  is a plan view showing the transfer vehicle having stopped at a pickup position. 
           [0022]      FIG. 5  is a plan view showing the transfer vehicle having stretched its arms. 
           [0023]      FIG. 6  is a plan view showing the transfer vehicle closing the arms to clamp an article. 
           [0024]      FIG. 7  is a plan view showing the transfer vehicle opening the arms to start pulling the article. 
           [0025]      FIG. 8  is a plan view showing the article that has been pulled in onto the transfer vehicle. 
           [0026]      FIG. 9  is a flowchart illustrating an algorithm used for performing article drop off. 
           [0027]      FIG. 10  is a plan view showing the article while the transfer vehicle is running. 
           [0028]      FIG. 11  is a plan view showing the transfer vehicle and the article that have stopped at a drop off position. 
           [0029]      FIG. 12  is a plan view showing the article being dropped off from the transfer vehicle to a rack. 
           [0030]      FIG. 13  is a plan view showing the article and the transfer vehicle after completion of the drop off. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    The following describes preferred embodiments of the present invention. The scope of the present invention is based on the claims, and is intended to be determined in accordance with the understanding of a person skilled in the art with reference to the description of the present invention and related art in the field of the present invention. 
         [0032]      FIGS. 1 to 13  show a transfer vehicle  4  according to a preferred embodiment of the present invention and its operation. The transfer vehicle  4  runs between a pair of right and left racks  6  and  7 . For example, the racks  6  and  7  are provided with their respective running rails  8 , and the transfer vehicle  4  runs on the running rails  8  by wheels  9  and a running motor  10  of the transfer vehicle  4 . In this preferred embodiment, the racks  6  and  7  are provided in multiple stages in the height direction, and a transfer vehicle  4  is provided for each stage. However, for example, the transfer vehicle  4  may be provided with an elevation frame such that the transfer vehicle  4  may transfer articles to and from a plurality of racks located at different levels of height. It is sufficient that the rack  6 ,  7  is provided at at least one of the right and left sides of the transfer vehicle  4 . The transfer vehicle  4  and the racks  6  and  7  collectively constitute an automated warehouse  2 . 
         [0033]    The transfer vehicle  4  includes a lateral pair of arm extending and retracting mechanisms  11   a  and  11   b , and reference numerals  12  and  13  denote their respective top arms. Each of the arms  12  and  13  is provided with a pair of hooks  14  and  15  at front and rear ends thereof. Note that the front-rear direction of the arms refers to the right-left direction as viewed from the transfer vehicle  4 . Also, the direction in which the spacing between the top arms  12  and  13  is changed is referred to as the opening and closing direction of the arms (the running direction of the transfer vehicle  4 ), and the right-left direction of the transfer vehicle  4  is referred to as the extending and retracting direction of the arms. Although the arm extending and retracting mechanisms  11   a  and  11   b  are three-stage arms configured to move middle arms  19  relative to the base and move the top arms  12  and  13  relative to the middle arms  19 , they may alternatively be two-stage or four-stage arms, for example. Reference numeral  16  denotes an arm opening and closing motor, an example of the arm opening and closing mechanism, configured to change the spacing between the top arms  12  and  13  by advancing or retracting the arm extending and retracting mechanism  11   b  along the running direction of the transfer vehicle  4 . Alternatively, both the arm extending and retracting mechanisms  11   a  and  11   b  may be advanced or retracted along the running direction of the transfer vehicle  4 . Reference numeral  17  denotes a nut that is fixed to the arm extending and retracting mechanism  11   b . An arm opening and closing motor  16  moves the arm extending and retracting mechanism  11   b  by rotating a screw shaft  18  meshed with the nut  17 . 
         [0034]      FIG. 2  shows a control system of the transfer vehicle  4 , and a controller  26  of the transfer vehicle  4  controls the running motor  10 , the arm opening and closing motor  16 , an arm extending and retracting motor  22 , and a hook opening and closing motor  24 . An arm extending and retracting motor  22  is provided for each of the arm extending and retracting mechanisms  11   a  and  11   b . A hook opening and closing motor  24  is provided for each of the four hooks  14 ,  14 ,  15 , and  15  such that the hooks  14  and  15  are opened or closed. A package sensor  20  detects whether the top arms  12  and  13  have clamped a package. For example, the package sensor  20  detects whether there is a sudden increase in the output torque upon contact with the package when the arm opening and closing motor  16  is closed at a constant velocity. Alternatively, the package sensor  20  detects whether there is a sudden decrease in the rotational speed of the arm opening and closing motor  16  upon contact with the package when the motor  16  is driven at a constant current. 
         [0035]    In accordance with the algorithms shown in  FIG. 3  and the subsequent drawing, the controller  26  controls the running motor  10 , the arm opening and closing motor  16 , the arm extending and retracting motor  22 , and the hook opening and closing motor  24 . The controller communicates with the warehouse controller  28 , which performs overall control of the automated warehouse  2 , and receives an instruction regarding transfer of articles from the warehouse controller  28 . The warehouse controller  28  includes a rack file  30 . The rack file  30  stores what size package is present in which location of the racks  6  and  7 , stores the proximal end position of a package along the length of the racks as the position of the package, and stores the size of the package and the width and depth of the package along the length of the racks. In addition to these, the rack file  30  stores the ID and the like of packages. Based on the data stored in the rack file  30 , the controller  26  may know what width package is picked up at which location. Further, when a package has been dropped off, the controller  26  reports the proximal end position of the package that has been dropped off and the width, the ID or the like of the package to the warehouse controller  28 , and the warehouse controller  28  updates the rack file  30  according to this data. The width of the package need not be reported. 
         [0036]      FIG. 3  shows an algorithm used to perform article pickup, and  FIGS. 4 to 8  schematically show an operation of the top arms  12  and  13 . The algorithm shown in  FIG. 3  is executed under control of the controller  26 . The transfer vehicle is notified of the proximal end position along the length of the racks  6  and  7  of a package  32  to be picked up and the width of the package  32  from the warehouse controller, and stops at a position suitable for performing article pickup. At this time, the spacing between the top arms  12  and  13  is set to be slightly larger than the package width, both the hooks  14  and  15  are opened, and at least the hooks  14 , which are located on the package  32  side (the distal end side), are opened. The allowance for the spacing between the top arms  12  and  13  with respect to the package width is, for example, about 5 mm to about 30 mm ( FIG. 4 ). 
         [0037]    Upon stoppage of the transfer vehicle  4 , the top arms  12  and  13  are advanced so as to protrude from the transfer vehicle  4 . At this time, the spacing between the top arms  12  and  13  is larger than the width of the package  32 , and therefore the arms  12  and  13  and the package  32  will not get caught on one another ( FIG. 5 ). Then, as shown in  FIG. 6 , the spacing between the top arms  12  and  13  is narrowed so as to clamp the package  32 . Then, when clamping is detected by the package sensor, the arm opening and closing motor is stopped so as to prevent an excessive pressure from being applied to the package. Concurrently therewith, for example, at least the hooks  14  at the distal end in the drop off direction are closed ( FIG. 6 ). 
         [0038]    After the top arms  12  and  13  have been positioned relative to the package  32  in the above-described manner, the spacing between the top arms  12  and  13  is slightly opened, for example, in an amount of about 3 mm to about 15 mm, thus providing a gap between the top arms  12  and  13  and the package  32  ( FIG. 7 ). Then, retraction of the top arms  12  and  13  onto the transfer vehicle  4  as shown in  FIG. 8  completes the article pickup. Note that the hooks  14  may be closed at any timing as long as they are closed before the start of retraction of the top arms  12  and  13 . When article pickup is performed as described above, the package  32  does not get caught on the top arms  12  and  13 , making it possible to prevent damage to the package  32  or damage to the top arms  12  and  13  and the like. Furthermore, the package  32  is nearly precisely positioned on the transfer vehicle  4 . 
         [0039]      FIG. 9  shows an algorithm used to perform article drop off, and  FIGS. 10 to 13  schematically show an operation of the top arms  12  and  13  in the process of the drop off. Note that the algorithm shown in  FIG. 9  is executed under control of the controller  26 . Upon completion of article pickup, the transfer vehicle  4  runs to the drop off position. The position has been notified by the warehouse controller  28 . To prevent the package  32  from swinging or protruding to the right or to the left from the transfer vehicle  4  during running, all the right and left hooks  14 ,  14 ,  15 , and  15  are closed, and the top arm  13  is moved toward the package  32  so as to clamp the package  32  by the top arms  12  and  13 . 
         [0040]    Immediately before the transfer vehicle  4  arrives at the drop off position, for example, after the transfer vehicle  4  has started decelerating in order to stop at the drop off position, more preferably when the transfer vehicle  4  has decelerated to a predetermined velocity or less, the top arm  13  is moved rearward in the running direction, thus providing a gap of, for example, about 3 mm to about 15 mm between the top arm  13  and the package  32  ( FIG. 11 ). Then, the hooks  15  at the distal end in the drop off direction are opened, and the top arms  12  and  13  are moved in the drop off direction so as to protrude from the transfer vehicle  4  ( FIG. 12 ). At this time, the spacing between the top arms  12  and  13  is slightly wider than the width of the package  32 , and therefore the package  32  will not get caught on the top arms  12  and  13 . Note that the hooks  15  at the distal end in the drop off direction may be opened, for example, before the top arms  12  and  13  start to retract, and more precisely, they may be opened before the hooks  15  have passed the position of the package  32  during retraction of the top arms  12  and  13 . 
         [0041]    When the package  32  has been moved to the rack  7  or the like where it is dropped off, for example, the top arms  12  and  13  are retracted onto the transfer vehicle  4  in a state in which the hooks  14  and  15  are opened. The hooks  14  may be either opened or closed as long as the position where the next article pickup is performed is in the same rack  7  where the previous article drop off was performed. If the position where the next article pickup is performed is the rack  6 , which is on the opposite side from the position where the previous article pickup was performed, the hooks  14  are opened before the next article pickup operation, for example, concurrently with retraction of the top arms  12  and  13 . The reason for this is that if the hooks  14  are opened when the hooks  14  are in contact with the package  32 , there is the possibility that the hooks may rub against the package. 
         [0042]    By performing the operation as described above, the package  32  will not get caught on the top arms  12  and  13  during article drop off. Since the package is clamped by the top arms  12  and  13  during running, the package does not undergo displacement or vibration. Furthermore, since the hooks  14  and  15  are closed, the package does not protrude from the transfer vehicle  4 . Also, since the package that has been pre-positioned by clamping during running is dropped off, the package may be dropped off at a precise position, so that the position of the package will not be imprecise. 
         [0043]    While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.