Patent Publication Number: US-11639275-B2

Title: Picking facility

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2020-021777 filed Feb. 12, 2020, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a picking facility. 
     2. Description of the Related Art 
     A picking facility for picking requested articles is used in a physical distribution facility including an automated warehouse, for example. An example of such a picking facility is a picking facility disclosed in JP 2017-30974A (Patent Document 1) that includes a first conveyor for transporting open top containers capable of containing target articles, and a second conveyor for transporting the target articles individually. In the picking facility disclosed in Patent Document 1, an operator takes out necessary target articles from containers (original packaging cases Cm) transported on the first conveyor (picking conveyor  32 ) and transfers them to the second conveyor (picked article transport conveyor  36 ), at a picking position. Then, the target articles transported on the second conveyor are placed in shipment containers (article collection cases Cs) according to destinations and then shipped. 
     In the picking facility disclosed in Patent Document 1, the height level of the transport face of the first conveyor is set to be higher than the height level of the transport face of the second conveyor. However, with such a configuration, when the target article is taken out from the container and transferred onto the second conveyor, the travel stroke of the target article in the vertical direction is the sum of the upward travel distance that is necessary to move the target article over the side wall of the container and the downward travel distance from the position to which the target article has been moved upward to the transport face of the second conveyor. Since the height level of the transport face of the second conveyor is lower than the height level of the transport face of the first conveyor, the travel stroke is inevitably two or more times as large as the upward travel distance. That is, the travel stroke of each target article during the picking operation is large, and thus there is room for improvement from the viewpoint of operation efficiency. 
     SUMMARY OF THE INVENTION 
     It is therefore desired to realize a picking facility with excellent operation efficiency. 
     A picking facility according to the present disclosure is a picking facility including: 
     a first conveyor for transporting a container that includes an opening portion provided on an upper side thereof and can contain an article; and 
     a second conveyor for transporting a target article, which is an article to be picked, 
     wherein a height level of a transport face of the first conveyor is set to be lower than a height level of a transport face of the second conveyor, and 
     a difference between the height level of the transport face of the second conveyor and the height level of the transport face of the first conveyor is determined based on a height of the container. 
     With this configuration, the transport face of the second conveyor can be arranged at an appropriate height in accordance with the height of the container located on the first conveyor. For example, the transport face of the second conveyor is arranged at a position near the upper end portion of the container located on the first conveyor. Accordingly, when the target article is taken out from the container and placed onto the second conveyor, the travel stroke of the target article in the vertical direction can be brought close to the upward travel distance that is necessary to move the target article over the side wall of the container. That is, the travel stroke of the target article in the vertical direction can be reduced. It should be noted that the same applies to a case where the target article transported on the second conveyor is placed in a container located on the first conveyor. Accordingly, a picking facility with excellent operation efficiency can be realized. 
     Further features and advantages of the technology according to the present disclosure will become apparent from the following description of illustrative and non-limiting embodiments with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a plan view of a picking facility according to an embodiment. 
         FIG.  2    is a side view of the picking facility. 
         FIG.  3    is a diagram for explaining a positional relationship in the vertical direction between a picking conveyor and an article collection conveyor. 
         FIG.  4    is a block diagram of a control unit. 
         FIG.  5    is a plan view of the picking facility. 
         FIG.  6    is another diagram for explaining a relationship in the vertical direction between the picking conveyor and the article collection conveyor. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     An embodiment of the picking facility will be described with reference to the drawings. It should be noted that, in the description below, the horizontal direction in  FIG.  1   , which is a plan view of a picking facility, is taken as the “X direction”, and the vertical direction in  FIG.  1    is taken as the “Y direction”. The vertical direction in  FIG.  2   , which is a side view of the picking facility, is taken as the “Z direction”. In this embodiment, the Z direction corresponds to the actual vertical direction. The X direction, the Y direction, and the Z direction intersect one another (at right angles in this embodiment). 
     A picking facility  1  is a facility for picking requested articles in a physical distribution facility including an automated warehouse  90  (see  FIG.  4   ), for example. The picking facility  1  of this embodiment is used to take out one or more target articles As from a plurality of articles A of the same type contained in a container C, perform this operation on a plurality of types of articles A (target articles As), and transfer a combination of the target articles As that have been taken out, to another container for article collection. 
     The container C is formed in a box shape including an opening portion Co provided on the upper side thereof. The container C is formed in a rectangular parallelepiped shape, and includes a side wall Cw that surrounds the periphery (four sides) thereof. The space delimited by the side wall Cw forms the inner space of the container C, and the articles A can be placed in this space. A plurality of types of containers C that each contain the articles A of the same type are stored in the automated warehouse  90 . One or more of these containers C are supplied to the picking facility  1  of this embodiment. It should be noted that the container C from which necessary target articles As have been taken out in the picking facility  1  is returned to the automated warehouse  90  again. 
     As shown in  FIG.  1   , the picking facility  1  of this embodiment includes a retrieval conveyor  10 , a picking conveyor  20 , a storage conveyor  30 , article collection conveyors  40 , a picking apparatus  50 , and a working space  60 . The picking conveyor  20  is arranged extending in the X direction. The retrieval conveyor  10 , the storage conveyor  30 , and the article collection conveyors  40  are arranged on the same side with respect to the picking conveyor  20  (on the upper side in  FIG.  1   ), and extend in parallel with one another in the Y direction. In this embodiment, the picking conveyor  20  corresponds to a “first conveyor”, and the article collection conveyors  40  correspond to a “second conveyor”. 
     The retrieval conveyor  10  transports the containers C containing the articles A that have been supplied from the automated warehouse  90 . The retrieval conveyor  10  of this embodiment includes a first retrieval conveyor  10 A and a second retrieval conveyor  10 B that are connected to each other in series. In the retrieval conveyor  10 , the upstream side of the first retrieval conveyor  10 A is connected to the automated warehouse  90 , and the downstream end portion of the second retrieval conveyor  10 B is connected to an upstream end portion  20   u  of the picking conveyor  20 . The retrieval conveyor  10  receives the containers C from the automated warehouse  90  and transports them in the Y direction to the picking conveyor  20 . In this embodiment, as shown in  FIG.  2   , the second retrieval conveyor  10 B extends in parallel with the XY plane, and the first retrieval conveyor  10 A is inclined such that a portion on the upstream side (automated warehouse  90  side) is located at a higher position. Various known conveyors such as a roller conveyor, a belt conveyor, and a slat conveyor can be used as the retrieval conveyor  10 . 
     The picking conveyor  20  transports the containers C containing the articles A that have been received from the retrieval conveyor  10 . The picking conveyor  20  transports the containers C in the X direction. The central area in the X direction of the picking conveyor  20  serves as a picking position P, and articles requested as per picking orders are picked at this picking position P. These articles requested as per picking orders are articles A to be picked and are referred to as “target articles As” in this embodiment. A downstream end portion  20   d  of the picking conveyor  20  is connected to the upstream end portion of the storage conveyor  30 . The picking conveyor  20  extends in parallel with the XY plane. Various known conveyors such as a roller conveyor, a belt conveyor, and a slat conveyor can be used as the picking conveyor  20 . 
     The storage conveyor  30  transports the containers C containing the articles A (non-target articles) other than the target articles As or the empty containers C that have been received from the picking conveyor  20 . The storage conveyor  30  of this embodiment includes a first storage conveyor  30 A and a second storage conveyor  30 B that are connected to each other in series. In the storage conveyor  30 , the upstream end portion of the first storage conveyor  30 A is connected to the downstream end portion  20   d  of the picking conveyor  20 , and the downstream side of the second storage conveyor  30 B is connected to the automated warehouse  90 . The storage conveyor  30  receives, from the picking conveyor  20 , the containers C that have been subjected to a picking operation, and transports them in the Y direction to the automated warehouse  90  side. In this embodiment, as shown in  FIG.  2   , the first storage conveyor  30 A extends in parallel with the XY plane, and the second storage conveyor  30 B is inclined such that a portion on the downstream side (automated warehouse  90  side) is located at a higher position. Various known conveyors such as a roller conveyor, a belt conveyor, and a slat conveyor can be used as the storage conveyor  30 . 
     The retrieval conveyor  10 , the picking conveyor  20 , and the storage conveyor  30  are arranged in an angular U-shape as a whole in a plan view (i.e., as viewed in the Z direction). 
     The article collection conveyors  40  transport the target articles As that have been taken out from the containers C at the picking position P. In this embodiment, the article collection conveyors  40  transport the target articles As individually in a state in which the target articles As are placed directly on the article collection conveyors  40 . The article collection conveyors  40  extend in the Y direction, and their end portions (upstream end portions) are adjacent to the picking conveyor  20 . In this manner, the article collection conveyors  40  transport the individual target articles As in the direction away from the picking conveyor  20  (i.e., toward the upper side in  FIG.  1   ). It is preferable that each of the article collection conveyors  40  is provided with a built-in lord cell for the purpose of confirming whether or not all of the requested target articles As have been taken out, and the like. 
     There is no particular limitation on the number of the article collection conveyors  40 , and a plurality of article collection conveyors  40  are provided in this embodiment. Specifically, three article collection conveyors  40  that are independent of each other, namely a first article collection conveyor  40 A, a second article collection conveyor  40 B, and a third article collection conveyor  40 C, are provided. These three article collection conveyors  40 A to  40 C extend in parallel and are adjacent to one another at regular intervals in the X direction. The retrieval conveyor  10  and the storage conveyor  30  are respectively arranged on the two sides in the X direction of the three article collection conveyors  40 A to  40 C with these article collection conveyors  40 A to  40 C being located therebetween. In other words, at least portions of the plurality of article collection conveyors  40  are arranged in the inner area of the angular U-shape formed by the retrieval conveyor  10 , the picking conveyor  20 , and the storage conveyor  30 . Such an arrangement configuration makes it possible to use space efficiently and reduce the size of the picking facility  1 . 
     Containers for article collection (article collection containers) are separately supplied to the downstream side of the article collection conveyors  40 , and the target articles As are placed in the article collection containers according to destinations and then shipped. In the case where a plurality of article collection conveyors  40  are provided as in this embodiment, picking operations according to destinations corresponding to the number of article collection conveyors  40  can be performed simultaneously. Accordingly, the overall picking efficiency can be improved. 
     As shown in  FIGS.  2  and  3   , in the picking facility  1  of this embodiment, the article collection conveyors  40  are arranged at positions higher than that of the picking conveyor  20 . Accordingly, a height level H 1  of a transport face  20   a  of the picking conveyor  20  is lower than a height level H 2  of the transport face  40   a  of each article collection conveyor  40 . It should be noted that, when the picking conveyor  20  is a roller conveyor, the transport face  20   a  of the picking conveyor  20  is a virtual plane that is in contact with all of the rollers, and when the picking conveyor  20  is a belt conveyor or slat conveyor, the transport face  20   a  thereof is the surface of the belt or slat. The same applies to the transport face  40   a  of the article collection conveyor  40 . 
     A difference ΔH (also referred to as a “conveyor level difference” hereinafter) between the height level H 2  of the transport face  40   a  of the article collection conveyor  40  and the height level H 1  of the transport face  20   a  of the picking conveyor  20  is determined based on a height H 3  of the container C. That is, the conveyor level difference ΔH is set to a height determined based on the height H 3  of the container C. The “height determined based on the height H 3  of the container C” as used herein is determined based on the height H 3  of the container C, and the concept thereof includes not only the height H 3  of the container C itself but also a height that is larger or smaller by a predetermined amount than the height H 3  of the container C. The “predetermined amount” in this case may be determined as appropriate in consideration of the structure of the picking facility  1 , the installation environment and the controllability of the picking facility  1 , the handleability of the container C and the target article As, and the like. 
     In this embodiment, as shown in  FIG.  3   , the difference ΔH between the height level H 2  of the transport face  40   a  of the article collection conveyor  40  and the height level H 1  of the transport face  20   a  of the picking conveyor  20  is set to match the height H 3  of the container C. More specifically, the positions in the Z direction (vertical direction) of the picking conveyor  20  and the article collection conveyors  40  are determined such that the conveyor level difference ΔH is equal to the height H 3  of the container C (ΔH=H 2 −H 1 =H 3 ). 
     With this configuration, the height level (=H 1 +H 3 ) of the upper end of a container C placed on the picking conveyor  20  is equal to the height level H 2  of the transport face  40   a  of the article collection conveyor  40 . Accordingly, when a target article As is taken out from the container C and placed on the article collection conveyor  40  during the picking operation, the travel stroke of the target article As in the Z direction (vertical direction) substantially includes only the upward travel distance (including a predetermined margin) that is necessary to move the target article As over the side wall Cw of the container C. That is, the individual target articles As taken out from the container C through the opening portion Co can be transferred onto the article collection conveyors  40  by merely moving them substantially horizontally (specifically, by moving them horizontally, and slightly vertically by an amount corresponding to the margin). Accordingly, it is possible to reduce the time required to pick the individual target articles As and to improve the overall picking efficiency. 
     The picking apparatus  50  picks the target article As from the articles A contained in the container C located at the picking position P, and transfers it to the article collection conveyor  40 . As shown in  FIGS.  1  and  2   , the picking apparatus  50  of this embodiment includes a holding portion  51  that can hold the target article As, a raising/lowering mechanism  52  that moves the holding portion  51  in the Z direction (vertical direction), and a movement mechanism  53  that moves the holding portion  51  along the XY plane. The movement mechanism  53  includes a first movement mechanism  54  that moves the holding portion  51  in the X direction, and a second movement mechanism  55  that moves the holding portion  51  in the Y direction. That is, the picking apparatus  50  includes the holding portion  51 , the raising/lowering mechanism  52 , the first movement mechanism  54 , and the second movement mechanism  55 . 
     The holding portion  51  is configured so as to be capable of holding the target article As. In this embodiment, the holding portion  51  includes a suction nozzle, and can hold the target article As through vacuum suction and release the target article As through air supply. The raising/lowering mechanism  52  includes a raising/lowering main body portion  52 A in which the holding portion  51  is fixed to the lower end portion. The raising/lowering main body portion  52 A is supported by a second slider  55 B of the second movement mechanism  55  in a state of being capable of sliding in the Z direction (vertical direction). 
     The first movement mechanism  54  includes a first guide rail  54 A extending in the X direction, and a first slider  54 B that is slidable along the first guide rail  54 A. It should be noted that the first guide rail  54 A is fixed to the installation surface or ceiling surface using a supporting member, suspending member, or the like, which are not shown in  FIG.  2   . A second guide rail  55 A of the second movement mechanism  55  is fixed to the first slider  54 B. The second movement mechanism  55  includes a second guide rail  55 A extending in the Y direction, and a second slider  55 B that is slidable along the second guide rail  55 A. The raising/lowering mechanism  52  (raising/lowering main body portion  52 A) is slidably supported by the second slider  55 B. 
     By sliding the first slider  54 B along the first guide rail  54 A, the holding portion  51  is moved in the X direction via the second movement mechanism  55  and the raising/lowering mechanism  52 . By sliding the second slider  55 B along the second guide rail  55 A, the holding portion  51  is moved in the Y direction via the raising/lowering mechanism  52 . By sliding the raising/lowering main body portion  52 A in the Z direction (vertical direction) relative to the second slider  55 B, the holding portion  51  fixed to the lower end portion of the raising/lowering main body portion  52 A is raised/lowered. In this manner, the picking apparatus  50  can move the holding portion  51  freely and three-dimensionally, and this function and the function of holding the target article As exhibited by the holding portion  51  can be utilized together to automatically transfer a target article As (automated picking). 
     It should be noted that the picking apparatus  50  is provided with a camera  58  as shown in  FIG.  2   . The camera  58  is installed facing downward at a position above the picking position P so as to be capable of taking, from above, pictures of the state inside the container C located at the picking position P. 
     The picking apparatus  50  is arranged at a position that overlaps the picking conveyor  20  and/or the article collection conveyors  40  in a plan view. It should be noted that a state in which two members “overlap each other in a plan view” means that at least a portion of one member and at least a portion of the other member overlap each other in a plan view. In this embodiment, as shown in  FIGS.  1  and  2   , the picking apparatus  50  is arranged at a position that is located above the picking conveyor  20  and the article collection conveyors  40  and overlaps the picking conveyor  20  and the article collection conveyors  40  in a plan view. More specifically, the picking apparatus  50  is arranged such that the first movement mechanism  54  overlaps the article collection conveyors  40  in a plan view and the second movement mechanism  55  overlaps at least the picking conveyor  20  in a plan view. 
     It should be noted that the second movement mechanism  55  is arranged overlapping the article collection conveyors  40  as well in a plan view depending on the position of the first slider  54 B in the X direction. Furthermore, the raising/lowering mechanism  52  is arranged overlapping the picking conveyor  20  in a plan view depending on the position of the second slider  55 B in the Y direction. 
     As described above, the picking apparatus  50  is arranged at a position that is located above the picking conveyor  20  and the article collection conveyors  40  and overlaps the picking conveyor  20  and the article collection conveyors  40  in a plan view, and therefore, a dedicated area for installation of the picking apparatus  50  is made unnecessary. By combining this configuration with the above-described configuration in which the retrieval conveyor  10 , the picking conveyor  20 , the storage conveyor  30 , and the article collection conveyors  40  are compactly arranged, the overall size of the picking facility  1  is effectively reduced. 
     The working space  60  is a space in which an operator W performs a picking operation. Since the picking facility  1  of this embodiment includes the working space  60 , manual picking by an operator W can be performed in addition to automated picking by the picking apparatus  50  (see  FIG.  5   ). In this embodiment, a work platform  61  on which the operator W stands and performs operations is installed in the working space  60 . It is preferable that the work platform  61  has a lifter function to enable height adjustment. 
     The working space  60  is arranged on a side opposite to the side on which the retrieval conveyor  10 , the storage conveyor  30 , and the article collection conveyors  40  are arranged with respect to the picking conveyor  20  (i.e., the lower side in  FIG.  5   ). Also, the working space  60  is arranged on a side opposite to the side on which the picking apparatus  50  is arranged with respect to the picking conveyor  20 . As described above, in this embodiment, the picking apparatus  50  and the working space  60  are respectively arranged on two sides of the picking conveyor  20  such that the picking conveyor  20  is located therebetween, and the picking apparatus  50  and the working space  60  do not overlap each other in a plan view. With such an arrangement configuration, even if the picking operation is switched from automated picking to manual picking while the picking apparatus  50  is stopped due to a failure thereof, for example, the picking apparatus  50  does not become an obstacle for the operator W performing an operation in the working space  60 . Accordingly, the manual picking can be smoothly performed. 
     The picking facility  1  includes a control unit  70  for controlling the portions of the picking facility  1 . The control unit  70  is constituted by a general-purpose computer such as a personal computer or a server computer including a central processing unit and a storage device such as a hard disk drive. As shown in  FIG.  4   , a rack controller  71 , a conveyor controller  72 , and a picking controller  73  are connected to the control unit  70  such that each controller can communicate with the control unit  70 . 
     The rack controller  71  is configured to control the operations of the automated warehouse  90 . In general, a guided vehicle including a transfer apparatus is provided in the automated warehouse  90 . The rack controller  71  controls the travel operation of the guided vehicle and the transfer operation of the transfer apparatus and thus executes processing for retrieving the containers C from the automated warehouse  90  and the processing for storing the containers C in the automated warehouse  90 . 
     The conveyor controller  72  is configured to control the operations of the retrieval conveyor  10 , the picking conveyor  20 , the storage conveyor  30 , and the article collection conveyors  40 . In general, each of the retrieval conveyor  10 , the picking conveyor  20 , the storage conveyor  30 , and the article collection conveyors  40  includes a driving motor for transporting articles to be transported (containers C herein) in the transport direction. The conveyor controller  72  controls the rotational operations of these driving motors and thus executes processing for transporting the containers C that have been retrieved from the automated warehouse  90  and are then returned to the automated warehouse  90  again, and processing for transporting the target articles As taken out at the picking position P for subsequent shipping. 
     The picking controller  73  is configured to control the operations of the picking apparatus  50 . As described above, the picking apparatus  50  includes the raising/lowering mechanism  52 , the first movement mechanism  54 , and the second movement mechanism  55 . In general, the picking apparatus  50  further includes driving motors for sliding the raising/lowering main body portion  52 A in the Z direction, the first slider  54 B in the X direction, and the second slider  55 B in the Y direction. The picking controller  73  controls the rotational operations of these driving motors and thus executes the processing for performing automated picking by the picking apparatus  50 . 
     It should be noted that the picking controller  73  is configured to be capable of recognizing the positions, the orientations, and the like of the target articles As in the container C by processing images taken by the camera  58 . The picking controller  73  controls the picking apparatus  50  based on the recognition results such that the automated picking by the picking apparatus  50  is appropriately performed. 
     Other Embodiments 
     (1) In the embodiment above, the configuration in which the retrieval conveyor  10 , the picking conveyor  20 , and the storage conveyor  30  are arranged in an angular U-shape in a plan view is described as an example. However, there is no limitation to such a configuration, and the positional relationships of the retrieval conveyor  10  and the storage conveyor  30  to the picking conveyor  20  in a plan view can be changed as appropriate. For example, at least one of the retrieval conveyor  10  and the storage conveyor  30  may also be connected to the picking conveyor  20  at an obtuse angle or an acute angle. In this case, the retrieval conveyor  10  and the storage conveyor  30  may also intersect each other in a plan view. 
     (2) In the embodiment above, the configuration in which the retrieval conveyor  10  and the storage conveyor  30  are arranged on the same side as the side on which the article collection conveyors  40  are arranged with respect to the picking conveyor  20  is described as an example. However, there is no limitation to such a configuration, and the retrieval conveyor  10  and the storage conveyor  30  may also be arranged on a side opposite to the side on which the article collection conveyors  40  are arranged with respect to the picking conveyor  20 . In this case, the retrieval conveyor  10  and the storage conveyor  30  may also be arranged such that the working space  60  is located therebetween in the X direction (first transport direction). Alternatively, the retrieval conveyor  10  and the storage conveyor  30  may also be lined up in a row with the picking conveyor  20 . 
     (3) In the embodiment above, the configuration in which only one picking conveyor  20  is provided is described as an example. However, there is no limitation to such a configuration, and a plurality of picking conveyors  20  that are independent of each other may also be provided and arranged in parallel at regular intervals in the Y direction. 
     (4) In the embodiment above, the configuration in which the three article collection conveyors  40 , which are independent of each other, are provided is described as an example. However, there is no limitation to such a configuration, and the number of the article collection conveyors  40  may also be two or four or more, for example. Alternatively, a configuration in which only one article collection conveyor  40  is provided may also be employed. 
     (5) In the embodiment above, the configuration in which the three article collection conveyors  40  are arranged in parallel with one another is described as an example. However, there is no limitation to such a configuration, and a plurality of article collection conveyors  40  may also be arranged such that the extension directions thereof radially extend or intersect in a plan view. 
     (6) In the embodiment above, the configuration in which the holding portion  51  of the picking apparatus  50  includes the suction nozzle and can hold the target article As through vacuum suction is described as an example. However, there is no limitation to such a configuration, and the holding portion  51  may also include a robot hand, holding claw, or the like that can hold the target article As. 
     (7) In the embodiment above, the configuration in which the picking apparatus  50  includes the holding portion  51 , the raising/lowering mechanism  52  that moves the holding portion  51  in the Z direction, the first movement mechanism  54  that moves the holding portion  51  in the X direction, and the second movement mechanism  55  that moves the holding portion  51  in the Y direction is described as an example. However, there is no limitation to such a configuration, and the picking apparatus  50  may also be constituted by an articulated robot arm or the like, for example. 
     (8) In the embodiment above, each article collection conveyor  40  may include a stopper  45  provided at the end portion near the picking conveyor  20  as shown in  FIG.  6   , for example. The stopper  45  protrudes upward from the transport face  40   a  of the article collection conveyor  40 . For example, even in a case where the target articles As have an external shape such as a spherical shape and thus are likely to roll, such a stopper  45  can prevent the target articles As transferred onto the article collection conveyor  40  from falling toward the picking conveyor  20  side. In the case of such a configuration, it is preferable to determine the positional relationship between the picking conveyor  20  and the article collection conveyor  40  in consideration of a height H 4  of the stopper  45  in addition to the height H 3  of the container C. In the example shown in  FIG.  6   , the difference ΔH between the height level H 2  of the transport face  40   a  of the article collection conveyor  40  and the height level H 1  of the transport face  20   a  of the picking conveyor  20  is set to match a value obtained by subtracting the height H 4  of the stopper  45  from the height H 3  of the container C. More specifically, the positions in the Z direction (vertical direction) of the picking conveyor  20  and the article collection conveyors  40  are determined such that the conveyor level difference ΔH is equal to the difference between the height  113  of the container C and the height  114  of the stopper  45  (ΔH=H 2 −H 1 =H 3 −H 4 ). 
     (9) In the embodiment above, the configuration in which the picking apparatus  50  is arranged at the position that overlaps the picking conveyor  20  and the article collection conveyors  40  and does not overlap the working space  60  in a plan view is described as an example. However, there is no limitation to such a configuration, and a configuration may also be employed in which the picking apparatus  50  is arranged on a side opposite to where the article collection conveyors  40  and the like are arranged with the picking conveyor  20  being located between the picking apparatus  50  and the article collection conveyors  40 , and does not overlap the article collection conveyors  40  in a plan view. Moreover, the picking apparatus  50  may be arranged overlapping the working space  60  in a plan view. 
     (10) In the embodiment above, the picking facility  1  that is configured such that the automated picking by the picking apparatus  50  is performed in normal cases and the manual picking by the operator W is performed only while the picking apparatus  50  is stopped due to a failure thereof or the like is mainly considered and described. However, there is no limitation to such a configuration, and the picking facility  1  may also be configured to be capable of actively switching between an automatic mode in which automated picking is performed and a manual mode in which manual picking is performed. 
     (11) In the embodiment above, the configuration in which the picking facility  1  includes the picking apparatus  50  is described as an example. However, there is no limitation to such a configuration, and a configuration may also be employed in which the picking facility  1  does not include the picking apparatus  50 , and manual picking is performed principally. 
     (12) In the embodiment above, the configuration in which the picking facility  1  includes the working space  60  is described as an example. However, there is no limitation to such a configuration, and a configuration may also be employed in which the picking facility  1  does not include the working space  60 , and automated picking is performed principally. 
     (13) The configurations disclosed in the above-described embodiments (including the above-mentioned embodiment and other embodiments; the same applies hereinafter) can also be used in combination with configurations disclosed in other embodiments as long as they are compatible with each other. Regarding the other configurations, the embodiments disclosed herein are illustrative in all respects and can be modified as appropriate without departing from the gist of the present disclosure. 
     Outline of the Embodiment 
     To summarize the description above, the picking facility according to the present disclosure preferably includes the following configurations. 
     The picking facility according to the present disclosure is a picking facility including: 
     a first conveyor for transporting a container that includes an opening portion provided on an upper side thereof and can contain an article; and 
     a second conveyor for transporting a target article, which is an article to be picked, 
     wherein a height level of a transport face of the first conveyor is set to be lower than a height level of a transport face of the second conveyor, and 
     a difference between the height level of the transport face of the second conveyor and the height level of the transport face of the first conveyor is determined based on a height of the container. 
     With this configuration, the transport face of the second conveyor can be arranged at an appropriate height in accordance with the height of the container located on the first conveyor. For example, the transport face of the second conveyor is arranged at a position near the upper end portion of the container located on the first conveyor. Accordingly, when the target article is taken out from the container and placed onto the second conveyor, the travel stroke of the target article in the vertical direction can be brought close to the upward travel distance that is necessary to move the target article over the side wall of the container. That is, the travel stroke of the target article in the vertical direction can be reduced. It should be noted that the same applies to a case where the target article transported on the second conveyor is placed in the container located on the first conveyor. Accordingly, a picking facility with excellent operation efficiency can be realized. 
     In an aspect, 
     it is preferable that the difference between the height level of the transport face of the second conveyor and the height level of the transport face of the first conveyor is set to match the height of the container. 
     With this configuration, when the target article is taken out from the container and placed onto the second conveyor, the travel stroke of the target article in the vertical direction can be minimized. As a result, it is possible to transfer, onto the second conveyor, the individual target articles taken out from the container by merely moving them horizontally, and slightly vertically. Accordingly, the operation efficiency can be further improved. 
     In an aspect, 
     it is preferable that the second conveyor is arranged extending in a direction intersecting a transport direction of the first conveyor in a state in which an end portion is adjacent to the first conveyor, and includes a stopper that is provided at an end portion near the first conveyor and protrudes upward from the transport face of the second conveyor, and 
     the difference between the height level of the transport face of the second conveyor and the height level of the transport face of the first conveyor is set to match a value obtained by subtracting a height of the stopper from the height of the container. 
     With this configuration, the second conveyor includes the stopper, and therefore, it is possible to prevent the target articles transferred onto the second conveyor from falling toward the first conveyor side. Moreover, with the configuration in which the second conveyor includes such a stopper, when the target article is taken out from the container and placed onto the second conveyor, the travel stroke of the target article in the vertical direction can be minimized. Accordingly, from these two viewpoints, the operation efficiency can be further improved. 
     In an aspect, 
     it is preferable that the picking facility further includes a picking apparatus that takes out the target article from the container, and 
     the picking apparatus includes a holding portion that can hold the target article, a movement mechanism that moves the holding portion in directions extending along the transport face of the first conveyor, and a raising/lowering mechanism that moves the holding portion in a vertical direction. 
     With this configuration, the target article can be moved freely and three-dimensionally in the state of being held by the holding portion, and automated picking by the picking apparatus can be appropriately performed. In such automated picking, when the picking apparatus transfers the target article, the magnitude of the travel stroke of the holding portion directly affects the operation efficiency. In this regard, with the technology disclosed in the present disclosure, the travel stroke of the holding portion in the vertical direction can be reduced, and the automated picking itself leads to greater efficiency, thus making it possible to significantly improve the operation efficiency. 
     It is sufficient that the picking facility according to the present disclosure can exhibit at least one of the above-described effects.