Patent Publication Number: US-2023150774-A1

Title: Transfer Device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-182466 filed Nov. 9, 2021, 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 transfer device configured to perform a transfer operation to move an article in a transfer direction between a supporter configured to support the article and a transfer target location. 
     2. Description of the Related Art 
     JP 2012-184085A (Patent Document 1) discloses an example of this type of transfer device. In the following, reference signs and names in parentheses in the description of related art are those of Patent Document 1. 
     The transfer device of Patent Document 1 includes a pair of advance-retreat sections (a pair of advance-retreat members  2 ) that moves back and forth in a transfer direction (front-back direction Y) and hooks ( 3 ) attached to respective ends of each advance-retreat section in the transfer direction. Each hook ( 3 ) is rotatable about an axis parallel with the transfer direction, and is caught on a face of an article (package W) that faces in the transfer direction while the hook ( 3 ) is in a protruding position in which the hook ( 3 ) protrudes in the width direction (left-right direction X) orthogonal to the transfer direction. This transfer device ( 1 ) transfers the article to and from a package storage rack ( 7 ) by moving the pair of advance-retreat sections ( 2 ) back and forth in the transfer direction with the hooks ( 3 ) thus caught on the article to be transferred. 
     The hooks ( 3 ) of the transfer device of Patent Document 1 each have a linear bar shape. For this reason, the hooks ( 3 ) may interfere with an article when the hooks ( 3 ) are in a retreat position in which the hooks ( 3 ) are parallel with the up-down direction, depending on the shape and/or the size of the article to be transferred. For example, if the article has a tapered shape that expands outward in the width direction while extending upward, a leading-end region of a hook ( 3 ) in the retreat position may come into contact with an upper part of the article. In this case, the transfer device ( 1 ) may not be able to appropriately transfer this article between the device and the transfer target location. 
     SUMMARY OF THE INVENTION 
     Therefore, in view of the foregoing, there is a demand for the realization of a transfer device capable of appropriately transferring an article without a hook interfering with the article. 
     A transfer device according to the present disclosure is a transfer device configured to perform a transfer operation to move an article in a transfer direction between a supporter configured to support the article and a transfer target location, the transfer device including: a first advance-retreat section configured to move back and forth in the transfer direction relative to the supporter; a second advance-retreat section located on a second side in a width direction, which is orthogonal to the transfer direction as viewed in an up-down direction, relative to the first advance-retreat section and configured to move back and forth in the transfer direction relative to the supporter, the second side in the width direction being one side in the width direction; a first hook supported by the first advance-retreat section and configured to change in position between a first retreat position and a first protruding position by pivoting about a first axis parallel with the transfer direction; and a second hook supported by the second advance-retreat section and configured to change in position between a second retreat position and a second protruding position by pivoting about a second axis parallel with the transfer direction, wherein the first retreat position is a position in which the first hook is parallel with the up-down direction, a leading-end section, which is a leading-end section of the first hook, is above the first axis, and the first hook does not overlap the article as viewed in the transfer direction, the first protruding position is a position in which the first leading-end section is on the second side in the width direction relative to a position of the first leading-end section in the first retreat position, and the first hook overlaps the article as viewed in the transfer direction, the second retreat position is a position in which the second hook is parallel with the up-down direction, a second leading-end section, which is a leading-end section of the second hook, is above the second axis, and the second hook does not overlap the article as viewed in the transfer direction, the second protruding position is a position in which the second leading-end section is on a first side in the width direction relative to a position of the second leading-end section in the second retreat position, and the second hook overlaps the article as viewed in the transfer direction, the first side in the width direction being another side in the width direction, the first hook has a first side-edge section that is an end edge on the second side in the width direction in the first retreat position, and the first side-edge section includes a partial region including at least the first leading-end section and having a shape that is, in the first retreat position, curved or bent to gradually extend toward the first side in the width direction while extending toward the first leading-end section, and the second hook has a second side-edge section that is an end edge on the first side in the width direction in the second retreat position, and the second side-edge section includes a partial region including at least the second leading-end section and having a shape that is, in the second retreat position, curved or bent to gradually extend toward the second side in the width direction while extending toward the second leading-end section. 
     Some articles transferred by the transfer device have an upper section whose dimension in the width direction is larger than the dimension of a lower section in the width direction. According to this configuration, it is easy to avoid interference between this type of article and leading-end-side regions of the first and second hooks in the retreat position. 
     Further, the first and second hooks in the retreat position need not be unnecessarily pivoted outward in the width direction to avoid such interference. Accordingly, it is possible to keep low the amount that each of the first the second hooks pivots for a position change between the retreat position and the protruding position. This makes it easy to shorten the time required to change the positions of the first and second hooks. 
     Further features and advantages of the transfer device will become apparent from the following description of exemplary and non-limiting embodiments that will be described with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an article transport facility. 
         FIG.  2    is a perspective view of a transfer device with advance-retreat sections in a withdrawn state. 
         FIG.  3    is a perspective view of the transfer device with the advance-retreat sections in a protruding state. 
         FIG.  4    shows hooks in a retreat position as viewed in a transfer direction. 
         FIG.  5    shows the hooks in a protruding position as viewed in the transfer direction. 
         FIG.  6    is a plan view schematically showing an article transfer operation. 
         FIG.  7    is a plan view schematically showing an article transfer operation. 
         FIG.  8    is a control block diagram. 
         FIG.  9    is a perspective view of a transfer device according to the second embodiment. 
         FIG.  10    shows the transfer direction according to the second embodiment as viewed in the transfer direction. 
         FIG.  11    shows the shape of hooks according to another embodiment as viewed in the transfer direction. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     A transfer device is a device that performs an article transfer operation. Hereinafter, embodiments of the transfer device will be described by taking as an example the case where an article transport facility in which articles are transported and stored is equipped with article transport vehicles  10  each of which includes the transport device. 
     First Embodiment 
     First, the first embodiment of a transfer device  1  will be described. 
     1. Overview of Article Transport Facility 
     An article transport facility  100  is equipped with an article transport vehicle 10 that includes the transfer device  1 , and an article storage rack  2  that includes a plurality of storage sections  13 , as shown in  FIG.  1   . 
     The article transport vehicle  10  transfers an article W in a specific direction in a horizontal plane. The article transport vehicle  10  in the present embodiment transfers the article W along a front face of the article storage rack  2 . The article storage rack  2  in the present embodiment has a multi-level structure with multi-level shelves  13 A in the up-down direction. The article transport vehicle  10  is disposed at each level of the article storage rack  2 . Note that  FIG.  1    only shows an article transport vehicle  10  provided at the uppermost level of the article storage rack  2 , out of a plurality of article transport vehicles  10 . 
     The article storage rack  2  includes a plurality of storage sections  13  disposed parallel with the up-down direction and a direction in which the travel path of the article transport vehicle  10  extends. Each storage section  13  is for storing an article W transported from the article transport vehicle  10 . The article storage rack  2  in the present embodiment has a plurality of shelves  13 A in the up-down direction that are disposed parallel with the rack-depth direction and the direction in which the travel path of the article transport vehicle  10  extends. The shelves  13 A constitute the storage sections  13 . An article W is put into a storage section  13  by being placed on a shelf  13 A. In the present embodiment, a pair of such article storage racks  2  is provided. The two article storage racks  2  face each other in the rack-depth direction with the travel path of the article transport vehicle  10  therebetween. Note that the rack-depth direction in the present embodiment is a direction orthogonal to the direction in which the travel path of the article transport vehicle  10  extends as viewed in the vertical direction. 
     The article transport facility  100  in the present embodiment is equipped with various devices for loading articles W onto the article storage rack  2 . Specifically, the article transport facility  100  is equipped with a loading conveyor  9 , a loading lift  4 , and loading relay conveyors  3 . The loading conveyor  9  transports an article W to be loaded onto the article storage rack  2  from the outside. The loading lift  4  receives the article W from the loading conveyor  9 , raises and lowers the article W, and delivers the article W to a loading relay conveyor  3 . Each loading relay conveyor  3  receives the article W from the loading lift  4  and delivers the article W to the article transport vehicle  10 . The loading relay conveyors  3  in this example are provided at respective levels of the article storage rack  2 . The loading lift  4  can deliver the article W to the loading relay conveyor  3  at each level by raising or lowering the article W. 
     The article transport facility  100  in the present embodiment is equipped with various devices for unloading articles W from the article storage rack  2 . Specifically, the article transport facility  100  is equipped with an unloading conveyor  14 , an unloading lift  7 , and unloading relay conveyors  8 . Each unloading relay conveyor  8  receives an article W from the article transport vehicle  10  and delivers the article W to the unloading lift  7 . The unloading relay conveyors  8  in this example are provided at the respective levels of the article storage rack  2 . The unloading lift  7  can move up and down. The unloading lift  7  can receive the article W from the unloading relay conveyor  8  at each level by moving up or down, and delivers the article W to the unloading conveyor  14 . The unloading conveyor  14  receives the article W from the unloading lift  7  and transports this article W to the outside. 
     2. Overview of Article Transport Vehicle 
     The article transport vehicle  10  includes a supporter  21  and the transfer device  1 , as shown in  FIGS.  2  and  3   . The transfer device  1  performs a transfer operation, namely an operation to move an article W in the transfer direction Y between the supporter  21  for supporting the article W and a transfer target location  11 . The transfer device  1  thus transfers the article W between the supporter  21  and the transfer target location  11 . The supporter  21  in the present embodiment is provided in the article transport vehicle  10 . Examples of the transfer target location  11  include a storage section  13 , a loading relay conveyor  3 , and an unloading relay conveyor  8 . 
     In the following, the direction in which the article W moves while the transfer device  1  performs the transfer operation will be referred to as a “transfer direction Y”, one side in the transfer direction Y as a “first side Y 1  in the transfer direction Y”, and the other side in the transfer direction Y as a “second side Y 2  in the transfer direction Y”. The direction orthogonal to the transfer direction Y as viewed in the up-down direction will be referred to as a “width direction X”, one side in the width direction X as a “first side X 1  in the width direction X”, and the other side in the width direction X as a “second side X 2  in the width direction X”. 
     The article transport vehicle  10  in the present embodiment includes a traveling body  12  (see  FIG.  1   ) that travels in the width direction X and a travel motor  12 M (see  FIG.  8   ) that drives the traveling body  12 . The traveling body  12  is driven by the travel motor  12 M and travels in the width direction X. The traveling body  12  in this example supports the supporter  21  and the transfer device  1 . 
     The supporter  21  in the present embodiment includes support plates  21   a  for supporting an article W from below, as shown in  FIGS.  2  and  3   . The support plates  21   a  are provided in correspondence with a first advance-retreat section  31  and a second advance-retreat section  41 , which will be described later. The support plates  21   a  are located inward, in the width direction X, of the first advance-retreat section  31  and the second advance-retreat section  41  (see  FIG.  4   ). In this example, an article W is placed on a pair of support plates  21   a  separated from each other in the width direction X. The article transport vehicle  10  transports, in the width direction X, the article W supported by the pair of support plates  21   a . 
     3. Transfer Device 
     The transfer device  1  includes the first advance-retreat section  31 , the second advance-retreat section  41 , first hooks  5 , and second hooks  6 , as shown in  FIGS.  2  and  3   . The transfer device  1  in the present embodiment also includes a spacing change mechanism  80 . 
     3-1. First Advance-Retreat Section 
     The first advance-retreat section  31  serves to move the first hooks  5  back and forth in the transfer direction Y relative to the supporter  21 . The first advance-retreat section  31  also serves to restrict movement of the article W in the width direction X and guide movement of the article W in the transfer direction Y together with the second advance-retreat section  41 . The first advance-retreat section  31  moves back and forth in the transfer direction Y relative to the supporter  21 , as shown in  FIGS.  2  and  3   . The first advance-retreat section  31  in the present embodiment moves back and forth in such a manner as to be capable of entering both a state of protruding toward the first side Y 1  in the transfer direction Y relative to the supporter  21  and a state of protruding toward the second side Y 2  in the transfer direction Y relative to the supporter  21 . A specific configuration of the first advance-retreat section  31  will be described below. 
     The first advance-retreat section  31  in the present embodiment includes a first opposing face  32  that opposes a first side face  71  of the article W that faces the first side X 1  in the width direction X, as shown in  FIGS.  2 ,  3 ,  4 , and  5   . The first opposing face  32  in this example opposes the first side face  71  of the article W supported by the supporter  21 , and also opposes the first side face  71  of the article W moving in the transfer direction Y relative to the supporter  21 . Further, the first advance-retreat section  31  has a first body  33 , which includes the first opposing face  32  opposing the first side face  71  of the article W that faces the first side X 1  in the width direction X, and a first advance-retreat mechanism  38  that moves the first body  33  back and forth. The first body  33  in this example is a member having a plate-like section extending in the transfer direction Y and the up-down direction. The first body  33  has the first opposing face  32  as a face that faces the second side X 2  in the width direction X. The first advance-retreat mechanism  38  includes a first fixed section  35 , a first relay section  36  provided between the first body  33  and the first fixed section  35 , and a first interlocking section  37  that interlocks the first relay section  36  and the first body  33 . 
     The first fixed section  35  in this example is fixed to the traveling body  12 . The first relay section  36  is so supported as to be movable in the transfer direction Y relative to the first fixed section  35 . The first body  33  is so supported as to be movable in the transfer direction Y relative to the first relay section  36 . The first interlocking section  37  moves the first body  33  relative to the first relay section  36  toward the side toward which the first relay section  36  moves in response to the first relay section  36  moving back or forth in the transfer direction Y relative to the first fixed section  35 . The first body  33  in the shown example is supported by the first relay section  36  via a linear movement guide mechanism  15 . Similarly, the first relay section  36  is supported by the first fixed section  35  via the linear movement guide mechanism  15 . That is, the first body  33  and the first relay section  36  are guided by the linear movement guide mechanism  15  and move back and forth in the transfer direction Y 
     The first advance-retreat section  31  in this example also includes a first driving mechanism  34 , as shown in  FIGS.  3 ,  4 , and  5   . The first driving mechanism  34  includes a drive shaft  34   a , an advance-retreat motor  34 M (see  FIG.  8   ) that drives the drive shaft  34   a  to rotate, a first belt  34   b  disposed parallel with the transfer direction Y and turned by the rotation of the drive shaft  34   a , and a first rack  34   c  that is provided in the first relay section  36  and meshes with the first belt  34   b  (see  FIGS.  4  and  5   ). The first driving mechanism  34  drives the drive shaft  34   a  to rotate with use of the advance-retreat motor  34 M, and turns the first belt  34   b  in a longitudinal direction thereof (transfer direction Y). The first driving mechanism  34  can thus move the first body  33  and the first relay section  36  toward the same side in the transfer direction Y 
     3-2. Second Advance-Retreat Section 
     The second advance-retreat section  41  is located on the second side X 2  in the width direction X relative to the first advance-retreat section  31 , as shown in  FIGS.  2  and  3   . The second advance-retreat section  41  in the present embodiment is separated from the first advance-retreat section  31  in the width direction X. An article W is disposed between the first advance-retreat section  31  and the second advance-retreat section  41  while being supported by the supporter  21 . The second advance-retreat section  41  serves to move the second hooks  6  back and forth in the transfer direction Y relative to the supporter  21 . The second advance-retreat section  41  moves back and forth in the transfer direction Y relative to the supporter  21 . The second advance-retreat section  41  in the present embodiment moves back and forth in such a manner as to be capable of entering both a state of protruding toward the first side Y 1  in the transfer direction Y relative to the supporter  21  and a state of protruding toward the second side Y 2  in the transfer direction Y relative to the supporter  21 . Also, the second advance-retreat section  41  moves back and forth in the transfer direction Y in synchronization with the first advance-retreat section  31 . A specific configuration of the second advance-retreat section  41  will be described below. Note that the second advance-retreat section  41  in the present embodiment has the same configuration as the first advance-retreat section  31 . 
     The second advance-retreat section  41  in the present embodiment includes a second opposing face  42  that opposes a second side face  72  of the article W that faces the second side X 2  in the width direction X, as shown in  FIGS.  2 ,  3 ,  4 , and  5   . The second opposing face  42  in this example opposes the second side face  72  of the article W supported by the supporter  21 , and also opposes the second side face  72  of the article W moving in the transfer direction Y relative to the supporter  21 . Further, the second advance-retreat section  41  has a second body  43 , which includes the second opposing face  42  opposing the second side face  72  of the article W that faces the second side X 2  in the width direction X, and a second advance-retreat mechanism  48  that moves the second body  43  back and forth. The second body  43  in this example is a member having a plate-like section extending in the transfer direction Y and the up-down direction. The second body  43  has the second opposing face  42  as a face that faces the first side X 1  in the width direction X. The second advance-retreat mechanism  48  includes a second fixed section  45 , a second relay section  46  provided between the second body  43  and the second fixed section  45 , and a second interlocking section  47  that interlocks the second relay section  46  and the second body  43 . 
     The second fixed section  45  in this example is supported by the traveling body  12  with the position of the second fixed section  45  in the transfer direction Y fixed. Also, the second fixed section  45  is separated from the first fixed section  35  and located on the second side X 2  in the width direction X relative the first fixed section  35 . The second relay section  46  is so supported as to be movable in the transfer direction Y relative to the second fixed section  45 . The second body  43  is so supported as to be movable in the transfer direction Y relative to the second relay section  46 . The second interlocking section  47  moves the second body  43  relative to the second relay section  46  toward the side toward which the second relay section  46  moves in response to the second relay section  46  moving back or forth in the transfer direction Y relative to the second fixed section  45 . The second body  43  in the shown example is supported by the second relay section  46  via a linear movement guide mechanism  15 . Similarly, the second relay section  46  is supported by the second fixed section  45  via the linear movement guide mechanism  15 . That is, the second body  43  and the second relay section  46  are guided by the linear movement guide mechanism  15  and move back and forth in the transfer direction Y 
     The second advance-retreat section  41  in this example also includes a second driving mechanism  44 , as shown in  FIGS.  3 ,  4 , and  5   . The second driving mechanism  44  includes the drive shaft  34   a , the advance-retreat motor  34 M (see  FIG.  8   ) that drives the drive shaft  34   a  to rotate, a second belt  44   b  disposed parallel with the transfer direction Y and turned by the rotation of the drive shaft  34   a , and a second rack  44   c  that is provided in the second relay section  46  and meshes with the second belt  44   b  (see  FIGS.  3  and  4   ). The second driving mechanism  44  drives the drive shaft  34   a  to rotate with use of the advance-retreat motor  34 M, and turns the second belt  44   b  in a longitudinal direction thereof (transfer direction Y). The second driving mechanism  44  can thus move the second body  43  and the second relay section  46  toward the same side in the transfer direction Y Thus, the second driving mechanism  44  in the present embodiment also uses the drive shaft  34   a  and the advance-retreat motor  34 M of the first driving mechanism  34 . Therefore, the first body  33 , the first relay section  36 , the second body  43 , and the second relay section  46  synchronously move back and forth in the transfer direction Y Note that the advance-retreat motor serving as a drive source of the second driving mechanism  44  may be a motor different from the advance-retreat motor serving as a drive source of the first driving mechanism  34 . 
     3-3. Spacing Change Mechanism 
     The spacing change mechanism  80  in the present embodiment changes the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  in the width direction X, as shown in  FIGS.  2  and  3   . The article transport facility  100  deals with articles W of various sizes. Therefore, the transfer device  1  is capable of transferring different types of articles W of different sizes. The spacing change mechanism  80  in the present embodiment changes the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  in the width direction X in correspondence with the dimension of the article W in the width direction X. The first advance-retreat section  31  and the second advance-retreat section  41  guide movement of the article W in the transfer direction Y so that the article W is appropriately transferred to the transfer target location  11 . 
     In the present embodiment, an article W whose first side face  71  protrudes toward the first side X 1  in the width direction X above an upper-end section  32   a  of the first opposing face  32  and whose second side face  72  protrudes toward the second side X 2  in the width direction X above an upper-end section  42   a  of the second opposing face  42  is referred to as a specific article Wt (see  FIGS.  4  and  5   ). The first side face  71  of the specific article Wt includes a first protruding face  71   a , which is a face located above the first opposing face  32  on the first side X 1  in the width direction X relative to a face below the first protruding face  71   a , and a first lower side face  71   b , which is a face below the first protruding face  71   a  (here, a face opposing the first opposing face  32 ). The first protruding face  71   a  is located at a position protruding toward the first side X 1  in the width direction X relative to the first lower side face  71   b . Similarly, the second side face  72  has a second protruding face  72   a , which is a face located above the second opposing face  42  on the second side X 2  in the width direction X relative to a face below the second side face  72   a , and a second lower side face  72   b , which is a face below the second protruding face  72   a  (here, a face opposing the second opposing face  42 ). The second protruding face  72   a  is located at a position protruding toward the second side X 2  in the width direction X relative to the second lower side face  72   b . In this example, the spacing change mechanism  80  changes the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  to a spacing corresponding to the dimension between the first lower side face  71   b  and the second lower side face  72   b  in the width direction X while the supporter  21  is supporting this type of specific article Wt. A specific configuration of the spacing change mechanism  80  will be described below. 
     The spacing change mechanism  80  includes a third belt  84 A disposed parallel with the width direction X, and a spacing change motor  84 M (see  FIG.  8   ) that rotates the third belt  84 A in the longitudinal direction thereof (width direction X), as shown in  FIGS.  2  and  3   . In this example, a part of the third belt  84 A is joined to the second fixed section  45  of the second advance-retreat section  41 . The spacing change mechanism  80  moves the second fixed section  45  joined to the third belt  84 A in the width direction X by driving the third belt  84 A with use of the spacing change motor  84 M. This changes the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  in the width direction X. The spacing change mechanism  80  in this example thus changes the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  by moving, in the width direction X, only the second advance-retreat section  41 , out of the first advance-retreat section  31  and the second advance-retreat  41 . Note that the spacing change mechanism  80  may alternatively move both the first advance-retreat section  31  and the second advance-retreat section  41  in the width direction X. 
     3-4. First Hook 
     Each first hook  5  is supported by the first advance-retreat section  31  and changes its position between a first retreat position P r   1  and a first protruding position P t   1  by pivoting about a first axis P 1  parallel with the transfer direction Y, as shown in  FIGS.  2 ,  3 ,  4 , and  5   . Each first hook  5  in the present embodiment pivots to change its position between the first retreat position P r   1  and the first protruding position P t   1 . 
     The first advance-retreat section  31  in the present embodiment supports a plurality of first hooks  5 . Specifically, the first hooks  5  are provided at both ends of the first body  33  in the transfer direction Y In this example, the first hook  5  is also provided at the center of the first body  33  in the transfer direction Y The first hooks  5  are driven by first pivot motors  50 M (see  FIG.  8   ) and pivot about the first axis P 1 . The plurality of (here, three) first hooks  5  are driven by the first pivot motors  50 M corresponding to the respective first hooks  5  and pivot independently of each other. 
     The first retreat position P r   1  is a position in which the first hook  5  is parallel with the up-down direction, a first leading-end section  51 , namely the leading-end section of the first hook  5  is located above the first axis P 1 , and the first hook  5  does not overlap the article W as viewed in the transfer direction Y, as shown in  FIG.  4   . In the present embodiment, the first hook  5  in the first retreat position P r   1  is parallel with the up-down direction, and the entire first hook  5  is located on the first side X 1  in the width direction X relative to the article W supported by the supporter  21 . Further, in the shown example, the entire first hook  5  in the first retreat position P r   1  is located on the outer side in the width direction X (first side X 1  in the width direction X) relative to the first opposing face  32 . The first leading-end section  51  in the first retreat position P r   1  is located above the first advance-retreat section  31 . The first hook  5  includes the aforementioned first leading-end section  51 , a first base  53  in which the first axis P 1  is located, and a first joint  54  that joins the first leading-end section  51  to the first base  53 . The first joint  54  in this example is a band-shaped section whose width gradually narrows as viewed in the transfer direction Y toward the first leading-end section  51 . The first leading-end section  51  is a section of the first hook  5  on the leading-end side relative to the first joint  54 , and has a larger width than the first joint  54  as viewed in the transfer direction Y The first base  53  is a section on the first axis P 1  side relative to the first joint  54 , and has a larger width than the first joint  54  as viewed in the transfer direction Y. That is, in the first retreat position P r   1 , the dimension of the first leading-end section  51  in the width direction X is larger than the dimension of a leading-end (upper-end) section of the first joint  54  in the width direction X, and the dimension of the first base  53  in the width direction X is larger than the dimension of a base-end (lower-end) section of the first joint  54  in the width direction X. In this example, the first leading-end section  51 , the first base  53 , and the first joint  54  are integrated. Further, the first hook  5  has a plate shape with an outer-edge section having a constant thickness in the transfer direction Y. 
     The first protruding position P t   1  is a position in which the first leading-end section  51  is located on the second side X 2  in the width direction X relative to the position of the first leading-end section  51  in the first retreat position P r   1 , and the first hook  5  overlaps the article W as viewed in the transfer direction Y, as shown in  FIG.  5   . In the first protruding position P t   1 , a part of the first hook  5  is located on the inner side in the width direction X (second side X 2  in the width direction X) relative to the first opposing face  32 . In the present embodiment, the first leading-end section  51  in the first protruding position P t   1  is located on the second side X 2  in the width direction X relative to the first advance-retreat section  31  and above the supporter  21  (here, the support plate  21   a ). Thus, upon the first hook  5  changing its position to the first protruding position P t   1 , the first hook  5  overlaps the article W supported by the supporter  21  as viewed in the transfer direction Y. In the first protruding position P t   1  in this example, the first joint  54  and the first leading-end section  51  of the first hook  5  are located at positions overlapping the article W as viewed in the transfer direction Y (see  FIG.  5   ). More specifically, a section of the first joint  54  excluding an end region on the first base  53  side and the first leading-end section  51  overlap the article W as viewed in the transfer direction Y. 
     A partial region E 1  of a first side-edge section  52 , which is an end edge, on the second side X 2  in the width direction X, of the first hook  5  in the first retreat position P r   1 , including at least the first leading-end section  51  has a shape that is, in the first retreat position P r   1 , curved or bent to gradually extend toward the first side X 1  in the width direction X while extending toward the first leading-end section  51 , as shown in  FIGS.  4  and  5   . In the present embodiment, the partial region E 1  of the first side-edge section  52  including at least the first leading-end section  51  has, in the first retreat position P r   1 , a shape that is curved to gradually extend toward the first side X 1  in the width direction X while extending toward the first leading-end section  51 . The first side-edge section  52  in this example includes an end edge of the first leading-end section  51  on the second side X 2  in the width direction X, an end edge of the first joint  54  on the second side X 2  in the width direction X, and an end edge of the first base  53  on the second side X 2  in the width direction X. The shape of the first hook  5  will be described below more specifically. 
     The first side-edge section  52  in the present embodiment has, in the first retreat position P r   1 , a first base-side region  52   a , which is a region on the first axis P 1  side relative to the upper-end section  32   a  of the first opposing face  32 , and a first leading-end-side region  52   b , which is a region on the first leading-end section  51  side relative to the upper-end section  32   a  of the first opposing face  32 , as shown in  FIGS.  4  and  5   . In the first retreat position P r   1  in this example, the first leading-end section  51  of the first hook  5  and a partial leading-end (upper-end) region of the first joint  54  protrude upward of the upper-end section  32   a  of the first opposing face  32 . Therefore, the first leading-end-side region  52   b  includes an end edge of the first leading-end section  51  on the second side X 2  in the width direction X, and an end edge of the partial leading-end (upper-end) region of the first joint  54  on the second side X 2  in the width direction X. The first base-side region  52   a  includes, in the first retreat position P r   1 , an end edge, on the second side X 2  in the width direction X, of a partial base-end (lower-end) region of the first joint  54 , which is located below the upper-end section  32   a  of the first opposing face  32 , and an end edge of the first base  53  on the second side X 2  in the width direction X. That is, the first base-side region  52   a  in the first retreat position P r   1  is a region of the first side-edge section  52  that is located on the base-end (lower-end) side relative to the first leading-end-side region  52   b . 
     In the first retreat position P r   1  in the present embodiment, the first base-side region  52   a  has a linear shape parallel with the first opposing face  32 , and the first leading-end-side region  52   b  has a shape that is curved or bent to gradually extend toward the first side X 1  in the width direction X while extending toward the first leading-end section  51 , as shown in  FIG.  4   . In this example, the first side-edge section  52  in the first retreat position P r   1  is curved, as a whole, toward the first side X 1  in the width direction X while extending toward the leading end (upper end), and has a curvature radius that gradually decreases toward the leading end (upper end). Therefore, the first base-side region  52   a  in the first retreat position P r   1  is slightly curved but has a substantially linear shape parallel with the first opposing face  32  (i.e., parallel with the up-down direction). In the shown example, a leading-end (upper-end) section of the first base-side region  52   a  is spaced apart from the first opposing face  32  toward the first side X 1  in the width direction X, and is slightly inclined relative to the first opposing face  32  (here, inclined about 5 degrees relative to the first opposing face  32 ). Thus, the “linear shape parallel with the first opposing face  32 ” includes any shape parallel with the first opposing face  32  as a whole even if this shape is curved or inclined to some extent. Meanwhile, the first leading-end-side region  52   b  is curved more than the first base-side region  52   a  and has a larger inclination angle relative to the first opposing face  32  than the first base-side region  52   a . Thus, the first leading-end-side region  52   b  has a shape that is curved to gradually extend toward the outer side in the width direction (i.e., the side away from the article W) while extending toward the first leading-end section  51 . As a result, the first leading-end-side region  52   b  in the first retreat position P r   1  is located on the first side X 1  in the width direction X relative to the first base-side region  52   a  and is located more on the first side X 1  in the width direction X while extending toward the first leading-end section  51 . 
     As mentioned above, the spacing change mechanism  80  in the present embodiment changes the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  in the width direction X to a spacing corresponding to the dimension of the article W in the width direction X in response to the supporter  21  supporting the article W. In the present embodiment, the first side-edge section  52  in the first retreat position P r   1  is located on the first side X 1  in the width direction X relative to the first side face  71  of the specific article Wt as viewed in the transfer direction Y while the first opposing face  32  is in contact with the first side face  71  of the specific article Wt, as shown in  FIG.  4   . In this example, the first base-side region  52   a  of the first side-edge section  52  in the first retreat position P r   1  is located on the first side X 1  in the width direction X relative to the first lower side face  71   b  of the first side face  71  of the article W. Further, the first leading-end-side region  52   b  of the first side-edge section  52  in the first retreat position P r   1  is located on the first side X 1  in the width direction X relative to the first protruding face  71   a  of the first side face  71  of the article W. The above-described shape of the first side-edge section  52  of the first hook  5  realizes the locational relationship between the first hook  5  and the article W in which the first protruding face  71   a  protruding toward the first side X 1  in the width direction X relative to the first lower side face  71   b  does not interfere with the first leading-end-side region  52   b  of the first side-edge section  52 . 
     In the first retreat position P r   1  in the present embodiment, a section of the first hook  5  below an upper end  33   a  of the first body  33  is so disposed as not to interfere with the first advance-retreat mechanism  38  that relatively moves in the transfer direction Y with respect to the first body  33 , as shown in  FIG.  4   . Furthermore, in the first retreat position P r   1  in this example, a section of the first hook  5  below the upper end  33   a  of the first body  33  is so disposed as not to interfere with the first driving mechanism  34  either. Specifically, the entire first joint  54  and the first base  53  of the first hook  5  are so disposed as not to interfere with both the first advance-retreat mechanism  38  and the first driving mechanism  34 . In the first retreat position P r   1  in the shown example, the first joint  54  and the first base  53  are so disposed as not to overlap, as viewed in the transfer direction Y, the first fixed section  35 , the first relay section  36 , and the first interlocking section  37  that constitute the first advance-retreat mechanism  38 , the first driving mechanism  34  (drive shaft  34   a , advance-retreat motors  34 M, first belt  34   b , first rack  34   c ), and the plurality of linear movement guide mechanisms  15 . In the first retreat position P r   1  in this example, the first joint  54  is parallel with the first opposing face  32 , thereby preventing the first hook  5  from interfering with the first advance-retreat mechanism  38  and the first driving mechanism  34  while the first body  33  is moving back and forth. 
     In this example, interference between a section of the specific article Wt above the first body  33  and the first hook  5  is avoided by disposing the first leading-end section  51  at a position overlapping the first relay section  36  as viewed in the up-down direction in the first retreat position P r   1 . Furthermore, the first hook  5  having a shape that is curved to gradually extend toward the first side X 1  in the width direction X while extending toward the first leading-end section  51  side (upward) in the first retreat position P r   1  as described above eliminates the need for disposing the entire first hook  5  on the first side X 1  in the width direction X in order to avoid interference with the specific article Wt, and allows only the first leading-end section  51  to be disposed on the first side X 1  in the width direction X relative to the specific article Wt. Accordingly, the first joint  54  and the first base  53  can be so disposed as not to interfere with the first advance-retreat mechanism  38  and the first driving mechanism  34 . 
     3-5. Second Hook 
     Each second hook  6  is supported by the second advance-retreat section  41  and changes its position between a second retreat position P r   2  and a second protruding position P t   2  by pivoting about a second axis P 2  parallel with the transfer direction Y, as shown in  FIGS.  2 ,  3 ,  4 , and  5   . Each second hook  6  in the present embodiment pivots to change its position between the second retreat position P r   2  and the second protruding position P t   2 . Note that the second hook  6  has the same configuration as the first hook  5 . 
     The second advance-retreat section  41  in the present embodiment supports a plurality of second hooks  6 . Specifically, the second hooks  6  are provided at both ends of the second body  43  in the transfer direction Y. In this example, the second hook  6  is also provided at the center of the second body  43  in the transfer direction Y. The second hooks  6  are driven by second pivot motors  60 M (see  FIG.  8   ) and pivot about the second axis P 2 . The plurality of (here, three) second hooks  6  are driven by the second pivot motors  60 M corresponding to the respective second hooks  6  and pivot independently of each other. 
     The second retreat position P r   2  is a position in which the second hook  6  is parallel with the up-down direction, a second leading-end section  61 , namely the leading-end section of the second hook  6  is located above the second axis P 2 , and the second hook  6  does not overlap the article W as viewed in the transfer direction Y, as shown in  FIG.  4   . In the present embodiment, the second hook  6  in the second retreat position P r   2  is parallel with the up-down direction, and the entire second hook  6  is located on the second side X 2  in the width direction X relative to the article W supported by the supporter  21 . Further, in the shown example, the entire second hook  6  in the second retreat position P r   2  is located on the outer side in the width direction X (second side X 2  in the width direction X) relative to the second opposing face  42 . The second leading-end section  61  in the second retreat position P r   2  is located above the second advance-retreat section  41 . The second hook  6  includes the aforementioned second leading-end section  61 , a second base  63  in which the second axis P 2  is located, and a second joint  64  that joins the second leading-end section  61  to the second base  63 . The second joint  64  in this example is a band-shaped section whose width gradually narrows as viewed in the transfer direction Y toward the second leading-end section  61 . The second leading-end section  61  is a section of the second hook  6  on the leading-end side relative to the second joint  64 , and has a larger width than the second joint  64  as viewed in the transfer direction Y. The second base  63  is a section on the second axis P 2  side relative to the second joint  64 , and has a larger width than the second joint  64  as viewed in the transfer direction Y. That is, in the second retreat position P r   2 , the dimension of the second leading-end section  61  in the width direction X is larger than the dimension of a leading-end (upper-end) section of the second joint  64  in the width direction X, and the dimension of the second base  63  in the width direction X is larger than the dimension of a base-end (lower-end) section of the second joint  64  in the width direction X. In this example, the second leading-end section  61 , the second base  63 , and the second joint  64  are integrated. Further, the second hook  6  has a plate shape with an outer-edge section having a constant thickness in the transfer direction Y. 
     The second protruding position P t   2  is a position in which the second leading-end section  61  is located on the first side X 1  in the width direction X relative to the position of the second leading-end section  61  in the second retreat position P r   2 , and the second hook  6  overlaps the article W as viewed in the transfer direction Y, as shown in  FIG.  5   . In the second protruding position P t   2 , a part of the second hook  6  is located on the inner side in the width direction X (first side X 1  in the width direction X) relative to the second opposing face  42 . In the present embodiment, the second leading-end section  61  in the second protruding position P t   2  is located on the first side X 1  in the width direction X relative to the second advance-retreat section  41  and above the supporter  21  (here, the support plate  21   a ). Thus, upon the second hook  6  changing its position to the second protruding position P t   2 , the second hook  6  overlaps the article W supported by the supporter  21  as viewed in the transfer direction Y. In the second protruding position P t   2  in this example, the second joint  64  and the second leading-end section  61  of the second hook  6  are located at positions overlapping the article W as viewed in the transfer direction Y (see  FIG.  5   ). More specifically, a section of the second joint  64  excluding an end region on the second base  63  side and the second leading-end section  61  overlap the article W as viewed in the transfer direction Y. 
     A partial region E 2  of a second side-edge section  62 , which is an end edge, on the first side X 1  in the width direction X, of the second hook  6  in the second retreat position P r   2 , including at least the second leading-end section  61  has a shape that is, in the second retreat position P r   2 , curved or bent to gradually extend toward the second side X 2  in the width direction X while extending toward the second leading-end section  61 , as shown in  FIGS.  4  and  5   . In the present embodiment, the partial region E 2  of the second side-edge section  62  including at least the second leading-end section  61  has, in the second retreat position P r   2 , a shape that is curved to gradually extend toward the second side X 2  in the width direction X while extending toward the second leading-end section  61 . The second side-edge section  62  in this example includes an end edge of the second leading-end section  61  on the first side X 1  in the width direction X, an end edge of the second joint  64  on the first side X 1  in the width direction X, and an end edge of the second base  63  on the first side X 1  in the width direction X. The shape of the second hook  6  will be described below more specifically. 
     The second side-edge section  62  in the present embodiment has, in the second retreat position P r   2 , a second base-side region  62   a , which is a region on the second axis P 2  side relative to the upper-end section  42   a  of the second opposing face  42 , and a second leading-end-side region  62   b , which is a region on the second leading-end section  61  side relative to the upper-end section  42   a  of the second opposing face  42 , as shown in  FIGS.  4  and  5   . In the second retreat position P r   2  in this example, the second leading-end section  61  of the second hook  6  and a partial leading-end (upper-end) region of the second joint  64  protrude upward of the upper-end section  42   a  of the second opposing face  42 . Therefore, the second leading-end-side region  62   b  includes an end edge of the second leading-end section  61  on the first side X 1  in the width direction X, and an end edge of the partial leading-end (upper-end) region of the second joint  64  on the first side X 1  in the width direction X. The second base-side region  62   a  includes, in the second retreat position P r   2 , an end edge, on the first side X 1  in the width direction X, of a partial base-end (lower-end) region of the second joint  64  that is located below the upper-end section  42   a  of the second opposing face  42 , and an end edge of the second base  63  on the first side X 1  in the width direction X. That is, the second base-side region  62   a  in the second retreat position P r   2  is a region of the second side-edge section  62  that is located on the base-end (lower-end) side relative to the second leading-end-side region  62   b . 
     In the second retreat position P r   2  in the present embodiment, the second base-side region  62   a  has a linear shape parallel with the second opposing face  42 , and the second leading-end-side region  62   b  has a shape that is curved or bent to gradually extend toward the second side X 2  in the width direction X while extending toward the second leading-end section  61 , as shown in  FIG.  4   . In this example, the second side-edge section  62  in the second retreat position P r   2  is curved, as a whole, toward the second side X 2  in the width direction X while extending toward the leading end (upper end), and has a curvature radius that gradually decreases toward the leading end (upper end). Therefore, the second base-side region  62   a  in the second retreat position P r   2  is slightly curved but has a substantially linear shape parallel with the second opposing face  42  (i.e., parallel with the up-down direction). In the shown example, a leading-end (upper-end) section of the second base-side region  62   a  is spaced apart from the second opposing face  42  toward the second side X 2  in the width direction X, and is slightly inclined relative to the second opposing face  42  (here, inclined about 5 degrees relative to the second opposing face  42 ). Thus, the “linear shape parallel with the second opposing face  42 ” includes any shape parallel with the second opposing face  42  as a whole even if this shape is curved or inclined to some extent. Meanwhile, the second leading-end-side region  62   b  is curved more than the second base-side region  62   a  and has a larger inclination angle relative to the second opposing face  42  than the second base-side region  62   a . Thus, the second leading-end-side region  62   b  has a shape that is curved to gradually extend toward the outer side in the width direction (i.e., the side away from the article W) while extending toward the second leading-end section  61 . As a result, the second leading-end-side region  62   b  in the second retreat position P r   2  is located on the second side X 2  in the width direction X relative to the second base-side region  62   a , and is located more on the second side X 2  in the width direction X while extending toward the second leading-end section  61 . 
     As mentioned above, the spacing change mechanism  80  in the present embodiment changes the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  in the width direction X to a spacing corresponding to the dimension of the article W in the width direction X in response to the supporter  21  supporting the article W. In the present embodiment, the second side-edge section  62  in the second retreat position P r   2  is located on the second side X 2  in the width direction X relative to the second side face  72  of the specific article Wt as viewed in the transfer direction Y while the second opposing face  42  is in contact with the second side face  72  of the specific article Wt, as shown in  FIG.  4   . In this example, the second base-side region  62   a  of the second side-edge section  62  in the second retreat position P r   2  is located on the second side X 2  in the width direction X relative to the second lower side face  72   b  of the second side face  72  of the article W. Further, the second leading-end-side region  62   b  of the second side-edge section  62  in the second retreat position P r   2  is located on the second side X 2  in the width direction X relative to the second protruding face  72   a  of the second side face  72  of the article W. The above-described shape of the second side-edge section  62  of the second hook  6  realizes the locational relationship between the second hook  6  and the article W in which the second protruding face  72   a  protruding toward the second side X 2  in the width direction X relative to the second lower side face  72   b  does not interfere with the second leading-end-side region  62   b  of the second side-edge section  62 . 
     In the second retreat position P r   2  in the present embodiment, a section of the second hook  6  below an upper end  43   a  of the second body  43  is so disposed as not to interfere with the second advance-retreat mechanism  48  that relatively moves in the transfer direction Y with respect to the second body  43 , as shown in  FIG.  4   . Furthermore, in the second retreat position P r   2  in this example, a section of the second hook  6  below the upper end  43   a  of the second body  43  is so disposed as not to interfere with the second driving mechanism  44  either. Specifically, the entire second joint  64  and the second base  63  of the second hook  6  are so disposed as not to interfere with both the second advance-retreat mechanism  48  and the second driving mechanism  44 . In the second retreat position P r   2  in the shown example, the second joint  64  and the second base  63  are so disposed as not to overlap, as viewed in the transfer direction Y, the second fixed section  45 , the second relay section  46 , and the second interlocking section  47  that constitute the second advance-retreat mechanism  48 , the second driving mechanism  44  (drive shaft  34   a , advance-retreat motors  34 M, second belt  44   b , second rack  44   c ), and the plurality of linear movement guide mechanisms  15 . In the second retreat position P r   2  in this example, the second joint  64  is parallel with the second opposing face  42 , thereby preventing the second hook  6  from interfering with the second advance-retreat mechanism  48  and the second driving mechanism  44  while the second body  43  is moving back and forth. 
     In this example, interference between a section of the specific article Wt above the second body  43  and the second hook  6  is avoided by disposing the second leading-end section  61  at a position overlapping the second relay section  46  as viewed in the up-down direction in the second retreat position P r   2 . Furthermore, the second hook  6  having a shape that is curved to gradually extend toward the second side X 2  in the width direction X while extending toward the second leading-end section  61  side (upward) in the second retreat position P r   2  as described above eliminates the need for disposing the entire second hook  6  on the second side X 2  in the width direction X in order to avoid interference with the specific article Wt, and allows only the second leading-end section  61  to be disposed on the second side X 2  in the width direction X relative to the specific article Wt. Accordingly, the second joint  64  and the second base  63  can be so disposed as not to interfere with the second advance-retreat mechanism  48  and the second driving mechanism  44 . 
     3-6. Stopper 
     The transfer device  1  in the present embodiment also includes first stoppers  91  that come into contact with the first hooks  5  in the first retreat position P r   1  from the first side X 1  in the width direction X, and second stoppers  92  that come into contact with the second hooks  6  in the second retreat position P r   2  from the second side X 2  in the width direction X, as shown in  FIG.  3   . The first stoppers  91  and the second stoppers  92  in this example have the same configuration. The first stoppers  91  restrain the first hooks  5  from further moving outward in the width direction (toward the first side X 1  in the width direction X) from the first retreat position P r   1 . Similarly, the second stoppers  92  restrict the second hooks  6  from further moving outward in the width direction (toward the second side X 2  in the width direction X) from the second retreat position P r   2 . The first stoppers  91  in this example are provided on the first advance-retreat section  31 . More specifically, a plurality of (here, three) first stoppers  91  are attached to an upper part of the first body  33  in correspondence with the respective first hooks  5 . Similarly, a plurality of (here, three) second stoppers  92  are attached to an upper part of the second body  43  in correspondence with the respective second hooks  6 . Each first stopper  91  in the shown example comes into contact with a section of the first joint  54  of a corresponding first hook  5  that is above the upper-end section  32   a  of the first opposing face  32  from the first side X 1  in the width direction X. Each second stopper  92  comes into contact with a section of the second joint  64  of a corresponding second hook  6  that is above the upper-end section  42   a  of the second opposing face  42  from the second side X 2  in the width direction X. 
     4. Control Unit 
     The article transport vehicle  10  includes a control unit H that controls each part, as shown in  FIG.  8   . The control unit H controls the operation of the traveling body  12  and the transfer device  1 . More specifically, the control unit H controls the travel motor  12 M, the advance-retreat motor  34 M, the first pivot motors  50 M, the second pivot motors  60 M, and the spacing change motor  84 M. The control unit H includes, for example, a processor such as a microcomputer, peripheral circuits such as memory, and the like. Each function is realized by cooperation of these pieces of hardware and programs executed on processors of a computer or the like. 
     The control unit H performs, as operations to transfer the article W, a pick-up operation to transfer the article W from the transfer target location  11  to the supporter  21 , and a delivery operation to transfer the article W from the supporter  21  to the transfer target location  11 , as shown in  FIGS.  6  and  7   . 
     When executing the pick-up operation, the control unit H controls the spacing change motor  84 M to set the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  in the width direction X to a spacing corresponding to the dimension, in the width direction X, of the article W to be transferred, as shown in  FIG.  6   . The control unit H then controls the advance-retreat motor  34 M to cause the first advance-retreat section  31  and the second advance-retreat section  41  to protrude toward the transfer target location  11  such that a first hook  5  and a second hook  6  are disposed at positions on the distal side in the transfer direction Y relative to the article W in the transfer target location  11  (see the left figure and the figure at the center in  FIG.  6   ). The control unit H thereafter controls the first pivot motors  50 M and the second pivot motors  60 M to change the position of the first hook  5  from the first retreat position P r   1  to the first protruding position P t   1  and change the position of the second hook  6  from the second retreat position P r   2  to the second protruding position P t   2  (see the figure at the center in  FIG.  6   ). The control unit H then controls the advance-retreat motor  34 M to cause the first advance-retreat section  31  and the second advance-retreat section  41  to retreat toward the supporter  21  (see the right figure in  FIG.  6   ). The control unit H thus executes the pick-up operation by pulling the article W toward the supporter  21  with the first hook  5  and the second hook  6  in contact with the article W in the transfer target location  11 . 
     When executing the delivery operation, the control unit H controls the spacing change motor  84 M to set the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  in the width direction X to a spacing corresponding to the dimension, in the width direction X, of the article W to be transferred, as shown in  FIG.  7   . The control unit H then controls the advance-retreat motor  34 M and adjusts the positions of the first advance-retreat section  31  and the second advance-retreat section  41  in such a manner as to dispose a first hook  5  and a second hook  6  at positions on the proximal side in the transfer direction Y relative to the article W on the supporter  21 . The control unit H thereafter controls the first pivot motors  50 M and the second pivot motors  60 M to change the position of the first hook  5  from the first retreat position P r   1  to the first protruding position P t   1  and change the position of the second hook  6  from the second retreat position P r   2  to the second protruding position P t   2  (see the left figure in  FIG.  7   ). The control unit H then controls the advance-retreat motor  34 M and causes the first advance-retreat section  31  and the second advance-retreat section  41  to protrude toward the transfer target location  11  (see the central figure in  FIG.  7   ). The control unit H thus executes the delivery operation by pushing the article W toward the transfer target location  11  with the first hook  5  and the second hook  6  in contact with the article W on the supporter  21 . The control unit H thereafter changes the position of the first hook  5  from the first protruding position P t   1  to the first retreat position P r   1 , and changes the position of the second hook  6  from the second protruding position P t   2  to the second retreat position P r   2  (see the right figure in  FIG.  7   ). 
     Second Embodiment 
     Next, the second embodiment of the transfer device will be described with reference to the drawings ( FIGS.  9  and  10   ). The following description of the transfer device in the present embodiment focuses on differences from the first embodiment. Features not specifically described are the same as the first embodiment, and a description thereof is omitted by assigning the same reference numerals. 
     The transfer device  1  in the present embodiment includes a first extension member  101  and a second extension member  201 , as shown in  FIGS.  9  and  10   . The first extension member  101  and the second extension member  201  in this example have the same configuration. 
     The first extension member  101  in the present embodiment is attached to an upper part of the first body  33 . The first extension member  101  in this example is attached to a position at which the first extension member  101  does not interfere with the first hooks  5  and the first stoppers  91 . Further, the first extension member  101  in the present embodiment has a third opposing face  102  that extends upward from the first opposing face  32  and parallel with the first opposing face  32  at the same position in the width direction X as the first opposing face  32 . That is, the third opposing face  102  is located on the second side X 2  in the width direction X relative to the first leading-end-side region  52   b  of each first hook  5 . The first extension member  101  in this example extends in the width direction X and the up-down direction, and the third opposing face  102  is a face of the first extension member  101  that faces the second side X 2  in the width direction X. The third opposing face  102  has a rectangular shape. The first extension member  101  in the shown example is an L-shaped bracket. The first extension member  101  is fixed to a face of the first body  33  that faces upward by a fastening member (not shown). 
     The second extension member  201  in the present embodiment is attached to an upper part of the second body  43 . The second extension member  201  in this example is attached to a position at which the second extension member  201  does not interfere with the second hooks  6  and the second stoppers  92 . The second extension member  201  has a fourth opposing face  202  that extends upward from the second opposing face  42  and parallel with the second opposing face  42  at the same position in the width direction X as the second opposing face  42 . That is, the fourth opposing face  202  is located on the first side X 1  in the width direction X relative to the second leading-end-side region  62   b  of each second hook  6 . The second extension member  201  in this example extends in the width direction X and the up-down direction, and the fourth opposing face  202  is a face of the second extension member  201  that faces the first side X 1  in the width direction X. The fourth opposing face  202  has a rectangular shape. The second extension member  201  in the shown example is an L-shaped bracket. The second extension member  201  is fixed to a face of the second body  43  that faces upward by a fastening member (not shown). 
     The transfer device  1  in the present embodiment has the first extension member  101  and the second extension member  201  in such a manner as to be capable of appropriately performing the operations to transfer the specific article Wt, as shown in  FIG.  10   . The specific article Wt in this example has a first protruding face  71   a  of the first side face  71  that protrudes toward the first side X 1  in the width direction X relative to the first lower side face  71   b  at a position that is above the upper-end section  32   a  of the first opposing face  32  and at least below the upper end of each first hook  5 , and a second protruding face  72   a  of the second side face  72  that protrudes toward the second side X 2  in the width direction X relative to the second lower side face  72   b  at a position that is above the upper-end section  42   a  of the second opposing face  42  and at least below the upper end of each second hook  6 . 
     In the example shown in  FIG.  10   , the position of the lower end of the first protruding face  71   a  of the specific article Wt is immediately above the upper-end section  32   a  of the first opposing face  32 . Similarly, the position of the lower end of the second protruding face  72   a  of the specific article Wt is immediately above the upper-end section  42   a  of the second opposing face  42 . Therefore, the third opposing face  102  opposes the first protruding face  71   a . Similarly, the fourth opposing face  202  opposes the second protruding face  72   a . If this type of specific article Wt is placed on the pair of support plates  21   a , the spacing change motor  84 M drives the first advance-retreat section  31  and the second advance-retreat section  41  to approach each other in the width direction X, then the third opposing  102  comes into contact with the first protruding face  71   a , and the fourth opposing face  202  comes into contact with the second opposing face  72   a . This can prevent a section of each first hook  5  that is above the upper-end section  32   a  of the first opposing face  32  from interfering with the first protruding face  71   a . Similarly, a section of each second hook  6  that is above the upper-end section  42   a  of the second opposing face  42  can be prevented from interfering with the second protruding face  72   a . 
     Other Embodiments 
     Next, other embodiments of the article transport facility will be described. 
     (1) The above embodiments have described examples of a configuration in which the partial region E 1  of the first side-edge section  52  that includes at least the first leading-end section  51  is, in the first retreat position P r   1 , curved to gradually extend toward the first side X 1  in the width direction X while extending toward the first leading-end section  51 , and the partial region E 2  of the second side-edge section  62  that includes at least the second leading-end section  61  is, in the second retreat position P r   2 , curved to gradually extend toward the second side X 2  in the width direction X while extending toward the second leading-end section  61 . However, there is no limitation to this configuration. The partial region E 1  of the first side-edge section  52  that includes at least the first leading-end section  51  may alternatively be, in the first retreat position P r   1 , bent to gradually extend toward the first side X 1  in the width direction X while extending toward the first leading-end section  51 , and the partial region E 2  of the second side-edge section  62  that includes at least the second leading-end section  61  may alternatively be, in the second retreat position P r   2 , bent to gradually extend toward the second side X 2  in the width direction X while extending toward the second leading-end section  61 .  FIG.  11    shows an example of this configuration. 
     The first side-edge section  52  of each first hook  5  in this example has a shape that is bent in a boundary area between the first base-side region  52   a  and the first leading-end-side region  52   b , as shown in  FIG.  11   . In the first retreat position P r   1 , the first base-side region  52   a  has a linear shape parallel with the first opposing face  32 , and the first leading-end-side region  52   b  has a linear shape that gradually extends toward the first side X 1  in the width direction X while extending toward the first leading-end section  51 . Similarly, the second side-edge section  62  of each second hook  6  has a shape that is bent in a boundary area between the second base-side region  62   a  and the second leading-end-side region  62   b . In the second retreat position P r   2 , the second base-side region  62   a  has a linear shape parallel with the second opposing face  42 , and the second leading-end-side region  62   b  has a linear shape that gradually extends toward the second side X 2  in the width direction X while extending toward the second leading-end section  61 . This configuration can also make it easy to prevent the first hooks  5  in the first retreat position P r   1  and the second hooks  6  in the second retreat position P r   2  from interfering with the specific article Wt. In the shown example, a bent section is formed in a part of the first side-edge section  52  of each first hook  5  and a part of the second side-edge section  62  of each second hook  6 . However, bent sections may alternatively be formed in a plurality of parts of the first side-edge section  52 . Similarly, bent sections may be formed in a plurality of parts of the second side-edge section  62  of each second hook  6 . 
     (2) The above embodiments have described examples of a configuration in which the first base-side region  52   a  of each first hook  5  in the first retreat position P r   1  has a linear shape parallel with the first opposing face  32 , and the second base-side region  62   a  of each second hook  6  in the second retreat position P r   2  has a linear shape parallel with the second opposing face  42 . However, the shapes of the first base-side region  52   a  and the second base-side region  62   a  are not limited thereto, and may alternatively have any of various other shapes. For example, each of the first base-side region  52   a  and the second base-side region  62   a  may have a shape that is curved in an arc shape or a wave shape. In this case as well, it is preferable that the entire first base-side region  52   a  in the first retreat position P r   1  is located on the outer side in the width direction (first side X 1  in the width direction X) relative to the first opposing face  32 . Similarly, it is preferable that the entire second base-side region  62   a  in the second retreat position P r   2  is located on the outer side in the width direction (second side X 2  in the width direction X) relative to the second opposing face  42 . 
     (3) The above embodiments have described examples of a configuration in which the transfer device  1  includes a spacing change mechanism  80  that changes the spacing between the first advance-retreat section  31  and the second advance-retreat section  41  in the width direction X. However, there is no limitation to this configuration, and the transfer device  1  need not include the spacing change mechanism  80 , for example. 
     (4) The above embodiments have described examples of a configuration in which the transfer device  1  includes first stoppers  91  that come into contact with the first hooks  5  in the first retreat position P r   1  from the first side X 1  in the width direction X, and second stoppers  92  that come into contact with the second hooks  6  in the second retreat position P r   2  from the second side X 2  in the width direction X. However, there is no limitation to this configuration, and the transfer device  1  need not include the first stoppers  91  or the second stoppers  92 . 
     (5) Configurations disclosed in the above-described embodiments (including the above embodiments and other embodiments; the same applied hereinafter) can also be applied in combination with configurations disclosed in any other embodiment as long as no contradiction arises. As for any other configurations, the embodiments disclosed herein are illustrative in all respects and can be appropriately modified without departing from the gist of the present disclosure. 
     Summary of The Above Embodiment 
     The summary of the above-described transfer device will be described below. 
     A transfer device is configured to perform a transfer operation to move an article in a transfer direction between a supporter configured to support the article and a transfer target location, and the transfer device includes: a first advance-retreat section configured to move back and forth in the transfer direction relative to the supporter; a second advance-retreat section located on a second side in a width direction, which is orthogonal to the transfer direction as viewed in an up-down direction, relative to the first advance-retreat section and configured to move back and forth in the transfer direction relative to the supporter, the second side in the width direction being one side in the width direction; a first hook supported by the first advance-retreat section and configured to change in position between a first retreat position and a first protruding position by pivoting about a first axis parallel with the transfer direction; and a second hook supported by the second advance-retreat section and configured to change in position between a second retreat position and a second protruding position by pivoting about a second axis parallel with the transfer direction, wherein the first retreat position is a position in which the first hook is parallel with the up-down direction, a leading-end section, which is a leading-end section of the first hook, is above the first axis, and the first hook does not overlap the article as viewed in the transfer direction, the first protruding position is a position in which the first leading-end section is on the second side in the width direction relative to a position of the first leading-end section in the first retreat position, and the first hook overlaps the article as viewed in the transfer direction, the second retreat position is a position in which the second hook is parallel with the up-down direction, a second leading-end section, which is a leading-end section of the second hook, is above the second axis, and the second hook does not overlap the article as viewed in the transfer direction, the second protruding position is a position in which the second leading-end section is on a first side in the width direction relative to a position of the second leading-end section in the second retreat position, and the second hook overlaps the article as viewed in the transfer direction, the first side in the width direction being another side in the width direction, the first hook has a first side-edge section that is an end edge on the second side in the width direction in the first retreat position, and the first side-edge section includes a partial region including at least the first leading-end section and having a shape that is, in the first retreat position, curved or bent to gradually extend toward the first side in the width direction while extending toward the first leading-end section, and the second hook has a second side-edge section that is an end edge on the first side in the width direction in the second retreat position, and the second side-edge section includes a partial region including at least the second leading-end section and having a shape that is, in the second retreat position, curved or bent to gradually extend toward the second side in the width direction while extending toward the second leading-end section. 
     Some of the articles transferred by the transfer device have an upper section whose dimension in the width direction is larger than the dimension of a lower section in the width direction. According to this configuration, it is easy to avoid interference between this type of article and a leading-end-side region of the first hook and a leading-end-side region of the second hook in the retreat position. 
     Further, the first hook and the second hook in the retreat position need not be unnecessarily pivoted outward in the width direction to avoid such interference. Accordingly, it is possible to keep low the amount that each of the first and second hooks pivots for a position change between the retreat position and the protruding position. This makes it easy to shorten the time required to change the positions of the first and second hooks. 
     It is preferable that the first advance-retreat section has a first opposing face opposing a first side face of the article that faces the first side in the width direction, the second advance-retreat section has a second opposing face opposing a second side face of the article that faces the second side in the width direction, the first side edge has, in the first retreat position, a first base-side region that is a region on the first axis side relative to an upper-end section of the first opposing face, and a first leading-end-side region that is a region on the first leading-end section side relative to the upper-end section of the first opposing face, the first side-edge section has a curved or bent shape according to which, in the first retreat position, (i) the first base-side region has a linear shape parallel with the first opposing face, and (ii) the first leading-end-side region gradually extends toward the first side in the width direction while extending toward the first leading-end section, the second side edge has, in the second retreat position, a second base-side region that is a region on the second axis side relative to an upper-end section of the second opposing face, and a second leading-end-side region that is a region on the second leading-end section side relative to the upper-end section of the second opposing face, and the second side-edge section has a curved or bent shape according to which, in the second retreat position, (i) the second base-side region has a linear shape parallel with the second opposing face, and (ii) the second leading-end-side region gradually extends toward the second side in the width direction while extending toward the second leading-end section. 
     According to this configuration, the first base-side region of the first hook in the first retreat position has a linear shape parallel with the first opposing face, and therefore does not protrude toward the article and can avoid interference with the article. Similarly, the second base-side region of the second hook in the second retreat position also has a linear shape parallel with the second opposing face, and therefore does not protrude toward the article and can avoid interference with the article. Meanwhile, the first leading-end-side region, which is a section of the first hook that is above the upper end of the first opposing face, has a shape that is curved or bent to gradually extend outward in the width direction while extending toward the first leading-end section. Therefore, the first leading-end-side region of the first hook can appropriately avoid interfering with an article having an upper section whose dimension in the width direction is larger than the dimension of a lower section in the width direction. Similarly, the second leading-end-side region, which is a section of the second hook that is above the upper end of the second opposing face, has a shape that is curved or bent to gradually extend outward in the width direction while extending toward the second leading-end section. Therefore, the second leading-end-side region of the second hook can appropriately avoid interfering with an article having an upper section whose dimension in the width direction is larger than the dimension of a lower section in the width direction. 
     It is preferable that the transfer device further includes a spacing change mechanism configured to change a spacing between the first advance-retreat section and the second advance-retreat section in the width direction, wherein the first advance-retreat section has a first opposing face opposing a first side face of the article that faces the first side in the width direction, the second advance-retreat section has a second opposing face opposing a second side face of the article that faces the second side in the width direction, the article whose first side face protrudes toward the first side in the width direction above an upper-end section of the first opposing face and whose second face protrudes toward the second side in the width direction above an upper-end section of the second opposing face is a specific article, the first side-edge section in the first retreat position is on the first side in the width direction relative to the first side face of the specific article as viewed in the transfer direction while the first opposing face is in contact with the first side face of the specific article, and the second side-edge section in the second retreat position is on the second side in the width direction relative to the second side face of the specific article as viewed in the transfer direction while the second opposing face is in contact with the second side face of the specific article. 
     According to this configuration, the first hook and the second hook in the retreat position can appropriately avoid interfering with the specific article having an upper section whose dimension in the width direction is larger than the dimension of a lower section in the width direction, even while the first opposing face and the second opposing face are in contact with this specific article. 
     It is preferable that first advance-retreat section has a first body including a first opposing face opposing a first side face of the article that faces the first side in the width direction, and a first advance-retreat mechanism configured to move the first body back and forth, the second advance-retreat section has a second body including a second opposing face opposing a second side face of the article that faces the second side in the width direction, and a second advance-retreat mechanism configured to move the second body back and forth, the first hook includes a section below an upper end of the first body, the section being so disposed, in the first retreat position, as not to interfere with the first advance-retreat mechanism relatively moving back and forth in the transfer direction with respect to the first body, and the second hook includes a section below an upper end of the second body, the section being so disposed, in the second retreat position, as not to interfere with the second advance-retreat mechanism relatively moving back and forth in the transfer direction with respect to the second body. 
     According to this configuration, the first hook in the first retreat position can avoid interfering with the first advance-retreat mechanism while the first body of the first advance-retreat section is moving back and forth. Similarly, the second hook in the second retreat position can avoid interfering with the second advance-retreat mechanism while the second body of the second advance-retreat section is moving back and forth. Accordingly, the first advance-retreat section and the second advance-retreat section can appropriately move back and forth. 
     It is preferable that the transfer device further includes: a first stopper configured to come into contact with the first hook in the first retreat position from the first side in the width direction, and a second stopper configured to come into contact with the second hook in the second retreat position from the second side in the width direction. 
     According to this configuration, the first hook and the second hook in the retreat position can be restrained from moving further outward in the width direction. 
     It is preferable that the first advance-retreat section has a first body including a first opposing face opposing a first side face of the article that faces the first side in the width direction, the second advance-retreat section has a second body including a second opposing face opposing a second side face of the article that faces the second side in the width direction, the first body includes an upper section to which a first extension member is attached, the first extension member has a third opposing face extending parallel with the first opposing face and upward from the first opposing face at a position corresponding to the first opposing face in the width direction, the second body includes an upper section to which a second extension member is attached, and the second extension member has a fourth opposing face extending parallel with the second opposing face and upward from the second opposing face at a position corresponding to the second opposing face in the width direction. 
     According to this configuration, even in the case of, for example, transferring an article having protruding sections protruding outward in the width direction relative to sections below the protruding sections in areas immediately above the upper-end sections of the first opposing face and the second opposing face, it is possible to prevent a region of the first hook in the retreat position that is immediately above the first opposing face and a region of the second hook in the retreat position that is immediately above the second opposing face from interfering with the protruding sections of the article. 
     Industrial Applicability 
     The technology according to the present disclosure can be used in transfer devices.