Article transport vehicle

Abstract

The transport vehicle 1 is equipped with a drop restriction device 2. The vehicle body 5 is equipped with a first cover 51, a second cover 52, and a cover connecting part 53. The drop restriction device 2 is equipped with a pair of drop restriction members 20 and a drive mechanism 30. Each of the pair of drop restriction members 20 is equipped with a support part, a pair of vertical extension parts 22, and a lower connecting part. The drive mechanism 30 drives the pair of drop restriction members 20 to move to a restricted position P1 and a released position P0. In the restricted position, the pair of vertical extension parts 22 are configured to overlap with the contained item Ws in the second direction view, and the lower connecting part overlaps with the contained item Ws in the vertical direction view. In the released position P0, the lower connecting part is configured not to overlap with the contained item Ws in the vertical direction view.

Description

Goods transport vehicle Field of the Invention The invention relates to an article transporting vehicle for transporting articles. Background of the Invention For example, Japanese Patent Application Laid-Open No. 2015-131702 (Patent Document 1) discloses an article transport vehicle having a pair of fall-restricting members. The article transport vehicle (ceiling transport vehicle 1) of Patent Document 1 comprises: a traveling portion (traveling moving portion 12) that travels on a travel track (2), a holding portion (support mechanism 19) that suspends and holds an article (transported article 6), a lifting portion (lifting operation mechanism 20) that supports the holding portion so that it can be freely raised and lowered, a cover portion (21) that covers the top and sides of the article located at the transport position, and a pair of drop-restricting members (a pair of drop-preventing bodies 27) that are separated in the traveling direction of the traveling portion. The pair of drop-restricting members are configured to be arranged below the article at the transport position and to approach and separate from each other along a horizontal plane. During the travel of the article transport vehicle, the pair of drop-restricting members are arranged at a position at the transport position that overlaps the article in a vertical direction. Therefore, even if the holding of the article by the holding portion is unintentionally released, the article can be supported by the pair of drop-restricting members, thereby preventing the article from falling below the pair of drop-restricting members. Summary of the Invention In the article transport vehicle of patent document 1, a pair of drop limiting members are support portions (supporting portions 21a) provided in a cantilevered state on the cover portion (21). Therefore, if the article retention by the retaining portion is released without intention, a bending moment will act on the pair of drop limiting members and the support portion in the cover portion (21) for supporting the drop limiting members. Therefore, in the case of assuming that a heavy article is to be transported, it is necessary to sufficiently ensure the strength of the drop limiting members and the support portion so as to be able to support the bending moment generated by supporting the article. For this reason, the so-called enlargement of the drop limiting members and the support portion will occur, which will become a major issue causing the enlargement or cost increase of the article transport vehicle. Therefore, it is desired to realize an article transport vehicle having a fall-restricting device having a structure that can easily ensure strength regardless of the weight of the article. The article transport vehicle disclosed herein is an article transport vehicle for transporting articles, comprising: a traveling portion having wheels; a vehicle body connected to the traveling portion and forming a storage space for storing the articles; a holding portion for holding the articles in a suspended state; a lifting portion for lifting and lowering the holding portion relative to the vehicle body, so that the articles held by the holding portion are lifted and moved to a storage position within the storage space and a lowered position below the storage space; and a fall limiting device for limiting the fall of the articles, i.e., the stored articles, located at the storage position, Taking a specific direction in the horizontal direction as a first direction, a direction perpendicular to the first direction in a vertical direction perspective as a second direction, one side of the first direction as a first side of the first direction, and the other side of the first direction as a second side of the first direction, the vehicle body comprises: a first cover portion for covering the first side of the first direction relative to the storage space; The second cover portion covers the second side in the first direction relative to the aforementioned storage space; and a cover connecting portion connects the first cover portion and the second cover portion at the upper side relative to the aforementioned storage space, the aforementioned fall limiting device includes a pair of fall limiting members and a driving mechanism for driving the pair of the aforementioned fall limiting members, each of the pair of the aforementioned fall limiting members includes: a supported portion supported by the aforementioned cover connecting portion; a pair of vertical extension portions arranged to be separated from each other on both sides of the aforementioned storage article in the aforementioned second direction and extending downward from the aforementioned supported portion; and a lower side connecting portion connecting the pair of the aforementioned vertical extension portions at a lower side than the aforementioned storage article, the aforementioned driving mechanism drives the pair of the aforementioned fall limiting members to move them to a restricted position and a released position, in the aforementioned restricted position, the pair of the aforementioned vertical extension portions of each of the pair of the aforementioned fall limiting members overlap with the aforementioned storage article in a second direction viewing angle along the aforementioned second direction, and the aforementioned lower side connecting portion of each of the pair of the aforementioned fall limiting members is arranged to overlap with the aforementioned storage article in a vertical direction viewing angle, In the released position, the lower connecting portion of each of the pair of drop preventing members is arranged outside the stored article in the first direction so as not to overlap with the stored article when viewed in the vertical direction. According to this structure, the supported portion of each of the pair of drop limiting members is supported by the upper cover connecting portion relative to the storage space in the vehicle body. Moreover, by a pair of vertical extensions extending downward from the supported portion, the lower connecting portion, which is lower than the stored item, is supported in a suspended state. Therefore, when the pair of drop limiting members are in the restricted position, even if the retention of the item by the retaining portion is unintentionally released, the item can be supported by the lower connecting portion of each of the pair of drop limiting members. Therefore, it is possible to avoid the item falling from the pair of drop limiting members. In addition, when the item is supported by the lower connecting portion, the load of the item acts as a tensile load in the vertical direction. The tensile load is a tensile load on the drop limiting member that is in a vertical position from the supported portion to the lower connecting portion. That is, it is possible to avoid a large bending moment acting on the drop limiting member and the supporting portion supporting the drop limiting member. Therefore, even when the weight of the article is large, the rigidity of the drop-limiting member and the support portion does not need to be greatly increased, and the strength required to support the article can be easily ensured. In addition, it is easy to seek miniaturization or lightweighting of the drop-limiting member and the support portion. In addition, according to this structure, when the pair of drop-limiting members are in the restricted position, each vertical extension portion is configured to overlap with the accommodated article when viewed from the second direction. Therefore, it is also possible to prevent the article or a part thereof from falling off in the second direction. In this way, according to this structure, an article transport vehicle can be realized that has a drop-limiting device with a structure that can easily ensure strength regardless of the weight of the article. Further features and advantages of the article transport vehicle will become apparent from the following description of the exemplary and non-limiting embodiments described with reference to the accompanying drawings. [Modes for carrying out the invention] The following describes an embodiment in which an article transport vehicle 1 is applied to an article transport facility 100 with reference to the drawings. In this embodiment, as shown in FIG1 , the article transport facility 100 includes an article transport vehicle 1 that travels along a travel path 3 and a processing device 10 that processes articles W contained therein. As shown in Figures 1 and 2, the article transport vehicle 1 is used to transport articles W. In this embodiment, the article transport vehicle 1 moves along a travel path 3 to transport the articles W. In this example, the travel path 3 is arranged along the ceiling, and a track R is provided along the travel path 3. That is, the article transport vehicle 1 is guided by the track R and travels along the travel path 3 to transport the articles W. Specifically, as shown in Figures 1 and 2, the track R is fixed to the ceiling while being suspended from the ceiling. In this example, a pair of tracks R is provided along the travel path 3. Thus, in this example, the article transport vehicle 1 is a ceiling transport vehicle that travels guided by a pair of tracks R suspended from the ceiling. Furthermore, the article transport vehicle 1 is not limited to a ceiling transport vehicle. In this example, the article transport equipment 100 is provided with a plurality of processing devices 10 (only one of them is shown in the example of FIG1 ). Furthermore, the article transport vehicle 1 transports the article W between the plurality of processing devices 10. Each of the plurality of processing devices 10 is provided with a port 10a. The article W to be processed by the processing device 10 is carried out and carried in and out of the port 10a. The article transport vehicle 1 stops at a position corresponding to the port 10a in the travel path 3 and transfers the article W between the port 10a. In this example, a container for accommodating semiconductor substrates (FOUP: Front Opening Unified Pod, wafer transfer box) is used as the article W to be transported. Furthermore, in the processing device 10, the semiconductor substrates accommodated in the article W are processed. Furthermore, in addition to the FOUP, the article W may be a mask storage container (so-called mask box) for accommodating a reticle. The following describes the structure of the article transport vehicle 1 in detail with reference to Figures 1 to 7 . In this description, a specific horizontal direction is referred to as the first direction X, a direction perpendicular to the first direction X from a vertical perspective is referred to as the second direction Y, one side of the first direction X is referred to as the first direction first side X1, and the other side of the first direction X is referred to as the first direction second side X2. In this example, the second direction Y is a horizontal direction perpendicular to the first direction X. As shown in Figures 1 and 2, an article transport vehicle 1 includes a traveling portion 4 having wheels 4a, a vehicle body 5 connected to the traveling portion 4 and defining a storage space S for storing articles W, a holding portion 6 for holding the articles W in a suspended state, a lifting portion 7 for raising and lowering the holding portion 6 relative to the vehicle body 5 and thereby moving the articles W held by the holding portion 6 to a storage position T1 within the storage space S and a lowered position T2 below the storage space S, and a fall restricting device 2 for restricting the articles W located at the storage position T1, i.e., the stored articles Ws, from falling. In this embodiment, the article transport vehicle 1 further includes a sliding portion 8 for sliding the articles W held by the holding portion 6 in a horizontal direction, and a control device H. As shown in Figures 1 and 2 , the traveling unit 4 includes wheels 4a that rotate on rails R and a traveling motor M1 for driving the wheels 4a. In the illustrated example, the traveling unit 4 includes a plurality of wheels 4a. The traveling motor M1 drives at least one of the plurality of wheels 4a to provide a propulsive force for moving the article transport vehicle 1 guided by the pair of rails R. Furthermore, in this embodiment, as shown in Figures 1 and 2 , the first direction X is a direction along the traveling direction of the traveling unit 4. That is, the direction along the traveling path 3 is the first direction X, and the article transport vehicle 1 travels along the first direction X. The holding portion 6 includes a pair of gripping claws 6a and a holding motor M2 for moving the pair of gripping claws 6a closer to or further away from each other (see FIG7 ). Furthermore, the holding portion 6 is configured to move the pair of gripping claws 6a closer to or further away from each other by driving the holding motor M2, thereby switching between a gripping state in which the pair of gripping claws 6a grip the article W and a gripping release state in which the gripping state is released. In this example, as shown in FIG2 , the article W includes an article body Wb and a held portion Wa located above the article body Wb. Furthermore, the holding portion 6 is configured to hold the held portion Wa of the article W, more specifically, to hold the article W in a suspended state by gripping the held portion Wa with the pair of gripping claws 6a. The sliding unit 8 includes a sliding body 8a that moves relative to the traveling unit 4 in the second direction Y, and a sliding motor M4 that moves the sliding body 8a in the second direction Y (see FIG. 7 ). The sliding unit 8 is configured so that the sliding body 8a is driven by the sliding motor M4 to move the sliding body 8a in the second direction Y, thereby moving the lifting unit 7, the holding unit 6, and the article W held by the holding unit 6 in the second direction Y. For example, when the port 10a in the processing device 10 is positioned offset in the second direction Y relative to the traveling path 3, the article W held by the holding unit 6 can be moved in the second direction Y to a position where the article W overlaps with the port 10a when viewed from the vertical direction. This allows the lifting unit 7 to appropriately transfer the article W to the port 10a. When the article transport vehicle 1 moves along the travel path 3, the lifting unit 7 raises the article W held by the holding unit 6 from the lowering position T2 to the storage position T1. Furthermore, when the lifting unit 7 transfers the article W between the article transport vehicle 1 and the port 10a, the lifting unit 7 lowers the article W held by the holding unit 6 from the storage position T1 to the lowering position T2. ​​In this example, as shown in Figures 1 and 2, the lifting unit 7 includes a pulley 7a supported by a sliding body 8a, a belt member 7b wound around the pulley 7a and connected to the holding unit 6 at the tip end, and a lifting motor M3 (see Figure 7) that rotates the pulley 7a to drive the belt member 7b. The lifting unit 7 rotates the pulley 7a in the forward direction by driving the lifting motor M3, thereby winding up the belt member 7b, thereby raising the holding unit 6 and the article W held by the holding unit 6 relative to the vehicle body 5. Furthermore, the lifting unit 7 rotates the pulley 7a in the reverse direction by driving the lifting motor M3, unwinding the belt member 7b, thereby lowering the holding unit 6 and the article W held therein relative to the vehicle body 5. In this manner, the article transport vehicle 1 transfers the article W between the port 10a and the holding unit 6 by raising and lowering the article W. As shown in Figures 1 and 2, in this embodiment, the vehicle body 5 is arranged below the traveling portion 4. In this example, the vehicle body 5 is suspended and supported by the traveling portion 4. Specifically, the traveling portion 4 is arranged on the upper side relative to the track R, and the vehicle body 5 is arranged on the lower side relative to the track R. Furthermore, in this embodiment, the vehicle body 5 is shaped to be open on at least one side in the second direction Y relative to the storage space S. In this example, the vehicle body 5 is shaped to be open on both sides and the lower side in the second direction Y relative to the storage space S. The specific structure of the vehicle body 5 will be described below. As shown in Figures 1 to 3 and 6 , the vehicle body 5 includes a first cover portion 51 that covers the first side X1 of the storage space S in the first direction, a second cover portion 52 that covers the second side X2 of the storage space S in the first direction, and a cover connecting portion 53 that connects the first and second cover portions 51 and 52 at the top of the storage space S. Furthermore, the storage space S is formed so as to be surrounded by the first cover portion 51, the second cover portion 52, and the cover connecting portion 53. In this embodiment, each of the first cover portion 51 and the second cover portion 52 is arranged so that the surfaces of the articles W (i.e., the stored articles Ws) held by the retaining portion 6 and stored in the storage space S, facing the first direction X, are opposed. Such covers are not provided on the sides and bottom of the storage space S in the second direction Y, but are open. Therefore, the stored articles Ws can slide relative to the storage space S toward the outside of the second direction Y via the sliding portion 8. Similarly, the stored articles Ws can be raised and lowered between the storage position T1 and the lowered position T2 by the lifting unit 7. Furthermore, in this embodiment, as shown in Figures 1 and 2, the cover connecting portion 53 is connected to the traveling portion 4. In this example, the article transport vehicle 1 further includes a connecting body 4d, and the cover connecting portion 53 is connected to the traveling portion 4 through the connecting body 4d (see Figures 2 and 3). Furthermore, as shown in Figure 2, the lifting unit 7, the sliding unit 8, and the holding portion 6 are arranged on the lower side of the cover connecting portion 53, and they are also supported on the traveling portion 4 by the connecting body 4d. Therefore, the storage space S for storing the articles W is formed below the area where the lifting unit 7, the sliding unit 8, and the holding portion 6 are arranged. The fall prevention device 2 is a device for preventing the article W from falling from the article transport vehicle 1, even if the article Ws held by the holding portion 6 is unintentionally released during the travel of the article transport vehicle 1. The specific structure of the fall prevention device 2 will be described below. As shown in Figures 1 to 5, the drop-stopping device 2 includes a pair of drop-stopping members 20 and a drive mechanism 30 for driving the pair of drop-stopping members 20. In this embodiment, the pair of drop-stopping members 20 are provided on the cover connecting portion 53. Furthermore, the pair of drop-stopping members 20 are spaced apart in the first direction X. Furthermore, when the retention of the stored article Ws by the retaining portion 6 is released, the pair of drop-stopping members 20 support the article W to prevent the article W from falling below the storage space S. As shown in Figures 2 to 6 , each of the pair of drop-limiting members 20 includes a supported portion 21 supported by the cover connecting portion 53, a pair of vertically extending portions 22 spaced apart on either side of the stored article Ws in the second direction Y and extending downward from the supported portion 21, and a lower connecting portion 24 connecting the pair of vertically extending portions 22 below the stored article Ws. In this embodiment, each of the pair of drop-limiting members 20 is arranged so as to surround both sides and the lower side of the storage space S in the second direction Y by means of the supported portion 21, the pair of vertically extending portions 22, and the lower connecting portion 24. In this example, the supported portion 21, the pair of vertically extending portions 22, and the lower connecting portion 24 are arranged outside the storage space S. Furthermore, in this example, each of the pair of drop-limiting members 20 has the same structure as the others. Therefore, the following description will focus on the configuration of one of the pair of fall-restricting members 20, and the description of the other will be omitted. In this embodiment, as shown in Figures 3 to 5, the supported portion 21 is supported on the cover connecting portion 53 through the drive mechanism 30. In addition, the supported portion 21 supports a pair of vertical extension portions 22 from above. In this example, the drop limiting member 20 has a pair of supported portions 21 corresponding to each of the pair of vertical extension portions 22. Moreover, the pair of supported portions 21 are separated and arranged in the second direction Y (more specifically, on both sides of the second direction Y relative to the stored items Ws). Moreover, each of the pair of supported portions 21 is connected to the corresponding vertical extension portion 22. In the examples of Figures 4 and 5, the pair of supported portions 21 are connected to the guide portion 32 of the drive mechanism 30 described later. Moreover, the connection portion of the guide portion 32 with the supported portion 21 serves as the support portion 41 described later. The details of the structure of such a drive mechanism 30 will be described later. In this embodiment, as shown in Figures 1, 2, 4 and 5, each of the pair of vertical extensions 22 is configured along the vertical direction. In addition, the pair of vertical extensions 22 are configured to overlap with each other when viewed from the second direction Y. Furthermore, the so-called "overlap" includes not only complete overlapping of regions but also overlapping of parts of regions. In this example, as described above, each of the pair of supported portions 21 supports a corresponding pair of vertical extensions 22 from the upper side. Specifically, the upper end of the vertical extension 22 is connected to the corresponding supported portion 21. Moreover, the vertical extension 22 is formed to extend downward from the supported portion 21. In addition, the lower end of the vertical extension 22 is configured below the bottom surface of the stored item Ws. In the examples of Figures 2, 4 and 5, the vertical extension 22 is a plate-like member configured along the vertical direction. Furthermore, in the restricted position P1 described later, each of the pair of vertical extensions 22 is positioned so as to face the surface of the article body Wb of the stored article Ws that faces the second direction Y. Furthermore, the lower end of each of the pair of vertical extensions 22 is positioned below the bottom surface of the stored article Ws and below the lower ends of the first cover portion 51 and the second cover portion 52 (in other words, below the storage space S). Furthermore, if the lower end of each of the pair of vertical extensions 22 is below the bottom surface of the stored article Ws, it is acceptable for the vertical extensions 22 to be positioned within the storage space S. In this case, the lower end of each of the pair of vertical extensions 22 is positioned below the bottom surface of the stored article Ws and above the lower ends of the first cover portion 51 and the second cover portion 52. Furthermore, in this example, the pair of vertical extensions 22 have the same structure, but they may also have different structures. Even in this case, it is preferable that the lower ends of the pair of vertically extending portions 22 are located at the same position in the vertical direction. In this example, each of the pair of vertically extending portions 22 is arranged in a posture along the vertical direction. However, for example, the pair of vertically extending portions 22 may be arranged in a posture inclined with respect to the vertical direction. In this embodiment, as shown in Figure 6, the lower connecting portion 24 connects the lower ends of the pair of vertically extending portions 22. That is, the lower connecting portion 24 is supported from above by the pair of vertically extending portions 22. In other words, the lower connecting portion 24 is supported from above by the pair of supported portions 21 through the pair of vertically extending portions 22. Furthermore, the lower connecting portion 24 is arranged below the bottom surface of the stored article Ws and is arranged along the second direction Y. In the illustrated example, the lower connecting portion 24 is a plate-shaped member extending along a horizontal plane. Moreover, at the limiting position P1 described later, the lower connecting portion 24 of each of the pair of drop-limiting members 20 is arranged to face the downward-facing surface of the article body Wb of the stored article Ws. Furthermore, in this example, although the lower connecting portion 24, the vertically extending portion 22, and the supported portion 21 are formed integrally, each of them may be formed from a separate object. As shown in Figure 2, the drive mechanism 30 drives the pair of drop-preventing members 20 to move between a restricted position P1 and a released position P0. The restricted position P1 prevents the pair of drop-preventing members 20 from dropping below the storage space S after the article W has been released from the retaining portion 6. In other words, the restricted position P1 supports the pair of drop-preventing members 20 from dropping below the storage space S after the article W has been released from the retaining portion 6. Furthermore, the released position P0 is the position of the pair of drop-preventing members 20 when the article transport vehicle 1 is transferring an article W between the port 10a. In the released position P0, the pair of drop-preventing members 20 are positioned so as not to interfere with the lifting portion 7, retaining portion 6, and sliding portion 8 performing transfer operations with respect to the port 10a, or with the article W already retained by the retaining portion 6. In this embodiment, the drive mechanism 30 moves the pair of drop-preventing members 20 from the restricted position P1 to the released position P0 when the article transport vehicle 1 is transferring an article W between the port 10a. Furthermore, the drive mechanism 30 moves the pair of drop-limiting members 20 from the release position P0 to the restriction position P1 when the article transport vehicle 1 holds the article W and moves along the travel path 3. In this embodiment, as shown in FIG2 , the drive mechanism 30 moves the supported portion 21 of each of the pair of drop-limiting members 20 toward the first direction X. Thus, each of the pair of drop-limiting members 20 is configured at any one of the restriction position P1 and the release position P0. In this example, the drive mechanism 30 moves each of the supported portions 21 that are configured to be separated in the first direction X toward the first direction X while simultaneously bringing them closer to and separating from each other. Furthermore, in this example, when the supported portion 21 (here, a pair of supported portions 21) moves toward the first direction X, the pair of vertical extension portions 22 and the lower connecting portion 24 also move together with the supported portion 21 toward the first direction X. That is, the driving mechanism 30 moves the pair of drop preventing members 20 toward and away from each other while moving the entire drop preventing member 20 in the first direction X. Hereinafter, the limiting position P1 and the releasing position P0 will be described in detail. As shown in Figures 2 and 6 , at the restricted position P1, the pair of vertical extensions 22 of each of the pair of drop-limiting members 20 overlap with the stored article Ws when viewed from the second direction Y along the second direction Y, and the lower connecting portion 24 of each of the pair of drop-limiting members 20 is positioned so as to overlap with the stored article Ws when viewed from the top and bottom. In this embodiment, at the restricted position P1, the pair of drop-limiting members 20 are positioned within a predetermined distance from the ends of the main body Wb of the stored article Ws in the first direction X. That is, the pair of vertical extensions 22 and the lower connecting portion 24 of each of the pair of drop-limiting members 20 are positioned within a predetermined distance from the ends of the main body Wb of the stored article Ws in the first direction X. The predetermined distance is set so that the pair of drop-limiting members 20 are positioned so as to appropriately support the article W (at the restricted position P1). In this example, at the restricted position P1, a pair of vertical extension portions 22 are configured so that a portion (in the illustrated example, an area below the center of the vertical extension portion 22) in the second direction Y perspective overlaps with the stored article Ws, and the lower connecting portion 24 is configured so that a portion (specifically, an area other than the two end portions in the second direction Y of the lower connecting portion 24) in the vertical direction perspective overlaps with the stored article Ws. Furthermore, in this example, as described above, at the restriction position P1, the pair of vertical extensions 22 are arranged so as to face the surface of the main body Wb of the stored article Ws that faces the second direction Y (see FIG2 ). Furthermore, at the restriction position P1, the lower connecting portion 24 is arranged so as to face the bottom surface of the main body Wb of the stored article Ws (see FIG6 ). Since the restriction position P1 is set so that the pair of drop-restricting members 20 are arranged as described above, even if the retention of the stored article Ws by the retaining portion 6 is unintentionally released, the released article W will fall onto the lower connecting portion 24 of each of the pair of drop-restricting members 20 and be appropriately supported by the lower connecting portion 24. Therefore, it is possible to prevent the article W from falling below the storage space S. Furthermore, for example, even if the article W that has been released from the article transport vehicle 1 is moved to one side of the second direction Y by the centrifugal force generated by traveling along the curved path in the traveling path 3, the article can be prevented from falling from one side of the second direction Y to a lower side than the storage space S because the article transport vehicle 1 contacts the upper and lower extension portions 22 on one side of the second direction Y of each of the pair of fall-limiting members 20. As shown in Figures 2 and 6 , in the release position P0, the lower connecting portion 24 of each of the pair of drop prevention members 20 is positioned outside the stored article Ws in the first direction X, so as not to overlap with the stored article Ws when viewed in the vertical direction. In this embodiment, in the release position P0, the pair of vertical extensions 22 of each of the pair of drop prevention members 20 are positioned outside the stored article Ws in the first direction X, so as not to overlap with the stored article Ws when viewed in the second direction Y. In this example, in the release position P0, the pair of drop prevention members 20 are positioned outside the object body Wb of the stored article Ws, a predetermined distance from either side in the first direction X. Therefore, in the release position P0, the pair of vertical extensions 22 are positioned so as to overlap with the storage space S when viewed in the second direction Y, so as not to overlap with the stored article Ws. Furthermore, in the released position P0, the lower connecting portion 24 of each of the pair of drop prevention members 20 is arranged so as to overlap with the storage space S, so as not to overlap with the stored articles Ws when viewed from the vertical direction. Therefore, when the articles W held by the holding portion 6 are raised or lowered between the storage position T1 and the lowered position T2, for example, they do not interfere with the lower connecting portion 24 of each of the pair of drop prevention members 20. Similarly, when the articles W held by the holding portion 6 are slid in the second direction Y, they do not interfere with the pair of vertically extending portions 22 of each of the pair of drop prevention members 20. As described above, in this example, the pair of drop-stopping members 20 move from the restriction position P1 toward opposite sides in the first direction X to reach the release position P0. That is, the release position P0 corresponding to each of the pair of drop-stopping members 20 is set on both outer sides of the stored article Ws in the first direction X. However, the release position P0 corresponding to each of the pair of drop-stopping members 20 may also be set to one side of the stored article Ws in the first direction X. In this case, the pair of drop-stopping members 20 reach the release position P0 by moving from the restriction position P1 toward the same side in the first direction X. As shown in Figures 2 to 5 , in this embodiment, the drive mechanism 30 includes a guide portion 32 that guides each supported portion 21 of the pair of fall prevention members 20 so that it can move freely in the first direction X, and a drive portion 35 that moves the pair of supported portions 21 to opposite sides of each other in the first direction X. In this example, the guide portion 32 and the drive portion 35 are provided on the cover connecting portion 53 (in the example of Figure 3 , on the upper surface of the cover connecting portion 53). In this example, as shown in Figures 2 to 5, the guide portion 32 includes a direct-acting guide mechanism 31. The direct-acting guide mechanism 31 is arranged along the first direction X, and the supported portion 21 of each of the pair of drop-limiting members 20 is connected to the direct-acting guide mechanism 31. In this way, each of the pair of drop-limiting members 20 is guided by the direct-acting guide mechanism 31 and moves in the first direction X. In the example of Figure 3, the pair of direct-acting guide mechanisms 31 are arranged separately in the second direction Y. Each of the pair of direct-acting guide mechanisms 31 includes a guide body 31a and a plurality of (here, two) moving bodies 31b. The guide body 31a is arranged so that the moving body 31b moves along the first direction X. Moreover, the moving body 31b is fixed with a pair of supported portions 21 of each of the pair of drop-limiting members 20. In the examples of Figures 4 and 5, the supported portion 21 is supported on the moving body 31b by being fixed to the moving body 31b from above. That is, the movable body 31b of the linear guide mechanism 31 functions as the support portion 41 supporting the supported portion 21. Furthermore, the linear guide mechanism 31 is here configured as a linear guide, but various known linear guide mechanisms such as ball splines and linear bushings may also be used. Furthermore, in this example, as shown in Figures 2 to 4 , the drive unit 35 includes a plurality of pulleys 35b supported by the cover connection portion 53, a drive belt member 35a wound around the plurality of pulleys 35b and connected to the linear guide mechanism 31, and a drop-limiting drive motor M6 that rotates the pulleys 35b to drive the drive belt member 35a. In the example of Figure 4 , the drive belt member 35a is wound around a plurality (here, two) of pulleys 35b spaced apart in the first direction X. Furthermore, one of the pair of drop-limiting members 20 is connected to the horizontal portion of the lower drive belt member 35a, while the other of the pair of drop-limiting members 20 is connected to the horizontal portion of the upper drive belt member 35a. Specifically, the drop-limiting members 20 are connected to the drive belt member 35a through a belt member support portion 23 provided on the upper portion of the vertically extending portion 22. Furthermore, the plurality of pulleys 35b rotate in the same direction, thereby moving the pair of drop-limiting members 20 closer together or further apart. In the example of Figure 3 , a pair of such drive belt members 35a are provided corresponding to the pair of linear guide mechanisms 31. The drive belt member 35a and the plurality of pulleys 35b are connected to a single drop-limiting drive motor M6 via a transmission mechanism 35c. The transmission mechanism 35c transmits the driving force of the drop-limiting drive motor M6 to the plurality of pulleys 35b. Furthermore, the drive belt member 35a rotates in conjunction with the rotation of the plurality of pulleys 35b, thereby causing the pair of drop-limiting members 20 to move closer together or further apart. In this embodiment, as shown in FIG7 , the control device H controls the traveling portion 4, the holding portion 6, the lifting portion 7, the sliding portion 8, and the drop-limiting device 2. The control device H includes a processor such as a microcomputer and peripheral circuits such as a memory. The functions of the control device H are realized by the cooperation of such hardware and software executed on the hardware such as the processor. The control device H is connected to a higher-level controller (not shown) that controls the entire article conveying equipment 100 so as to be able to communicate with each other. The control device H is configured to obtain instructions from the higher-level controller (not shown) in the instruction acquisition unit 11, and to control the traveling portion 4, the holding portion 6, the lifting portion 7, the sliding portion 8, and the drop-limiting device 2 according to the content of the obtained instructions. In this example, the control device H performs transport control for transporting articles W between a plurality of processing devices 10 and transfer control for transferring articles W to and from the port 10 a. During transport control, the control device H controls the travel unit 4 (travel motor M1) in response to transport commands from the host controller, moving the article transport vehicle 1 toward the processing device 10 at the transfer destination. At this point, the control device H controls the drop-restricting device 2 (drop-restricting drive motor M6) to maintain the pair of drop-restricting members 20 at the restricted position P1. The control device H then stops the article transport vehicle 1 at a parking position corresponding to the port 10a in the processing device 10 at the transfer destination. Therefore, even if the article W held by the retaining unit 6 is unintentionally released during the movement of the article transport vehicle 1, the article W is supported by the lower connecting portion 24 of each of the pair of drop-restricting members 20, preventing the article W from falling below the storage space S, that is, from falling from the article transport vehicle 1. Furthermore, even if, for example, the article W is released from its hold and moves toward either side of the second direction Y due to traveling along a curved path in the traveling path 3 and receiving an external impact, the movement toward the outside of the storage space S in the second direction Y is restricted by the upper and lower extension portions 22 of each of the pair of drop-limiting members 20, thereby preventing the article W from falling from either side of the second direction Y relative to the storage space S. Here, as shown in Figures 3, 4, and 5, each of the pair of drop-stopping members 20 is supported from above by the support portion 41 (here, the plurality of movable bodies 31b) in a vertically oriented position. Furthermore, the released object W is supported from below by the lower end portion of each of the pair of drop-stopping members 20, namely the lower connecting portion 24. Therefore, compared to a case where the pair of drop-stopping members 20 are supported in a cantilevered manner by each of the first cover portion 51 and the second cover portion 52, a large bending moment can be avoided from acting on the support portion 41 supporting the drop-stopping members 20. Therefore, even when the weight of the transported object W is large, the required strength to support the object W can be easily ensured without significantly increasing the rigidity of the drop-stopping members 20 or the supporting member. Therefore, regardless of the weight of the object W, the pair of drop-stopping members 20 can easily and appropriately support the released object W. Furthermore, it is easy to avoid increasing the size of the fall prevention member 20 or the support portion 41 in order to ensure the strength required to support the article W. The control device H performs transfer control on the article transport vehicle 1 parked at the port 10a to be transferred. When transferring an article W between the port 10a and the article transport vehicle 1, the control device H controls the drop-restricting device 2 to move the pair of drop-restricting members 20 from the restriction position P1 to the release position P0. This prevents interference between the article W held in the holding portion 6 and the pair of drop-restricting members 20 when transferring the article W between the article transport vehicle 1 and the port 10a. With the pair of drop-restricting members 20 in the release position P0, the control device H controls the lifting unit 7 (lifting motor M3) to lift the article W between the storage position T1 and the lowered position T2. ​​Here, when the port 10a is offset from the rail R along the travel path 3, the control device H controls the sliding unit 8 (sliding motor M4) to slide the article W in the second direction Y. Thus, the control device H moves the pair of drop preventing members 20 from the limiting position P1 to the releasing position P0 during transfer control, thereby enabling transfer of the article W between the port 10 a without interference with the pair of drop preventing members 20 . [Other Embodiments] Next, other embodiments of the article transport vehicle will be described. (1) In the above embodiment, the fall restricting device 2 is described as including a pair of fall restricting members 20 , but the present invention is not limited thereto. For example, the fall restricting device 2 may include three or more fall restricting members 20 . (2) In the above-described embodiment, the article transport vehicle 1 is described as an example in which the pair of drop-restricting members 20 are moved from the release position P0 to the restriction position P1 when transporting the article W. Even if the retention of the stored article Ws by the retaining portion 6 is released, the lower connecting portion 24 of each of the pair of drop-restricting members 20 can support the article W. However, the present invention is not limited to such a configuration. For example, the article transport vehicle 1 may also include a swing prevention mechanism 60 in addition to the pair of drop-restricting members 20. In this way, vibration generated during the movement of the article transport vehicle 1 is absorbed by the swing prevention mechanism 60, thereby reducing the vibration transmitted to the stored article Ws. Therefore, damage to the stored article Ws due to vibration can be avoided. Such an example is shown in FIG8 . In the example of FIG8 , each of the first cover portion 51 and the second cover portion 52 is provided with a swing prevention body 60a and a swing prevention body support portion 60b that supports the swing prevention body 60a, serving as the swing prevention mechanism 60. In the illustrated example, the anti-sway mechanism 60a is a roller that rotates about an axis extending in the vertical direction. The anti-sway mechanism support portion 60b, which supports the roller for free rotation, is mounted on the first cover portion 51 and the second cover portion 52 so as to be movable in the first direction X. Furthermore, when the article transport vehicle 1 is in motion, the anti-sway mechanism support portion 60b of each of the first cover portion 51 and the second cover portion 52 protrudes inward in the first direction X within the storage space S and abuts against the side surface (facing the first direction X) of the main body Wb of the stored article Ws. It is preferable to use a common drive source for the anti-sway mechanism 60 and the drive source (in the above-described embodiment, the drop-limiting drive motor M6) that drives the pair of drop-limiting members 20. Furthermore, the anti-sway mechanism 60a may also be configured to include an elastic member. This allows for more effective absorption of vibrations transmitted to the stored article Ws. (3) In the above-described embodiment, the supported portion 21 of each of the pair of drop limiting members 20 is moved in the first direction X by the drive mechanism 30, thereby causing the pair of vertically extending portions 22 of each of the pair of drop limiting members 20 to move in the first direction X. Furthermore, in the release position P0, the pair of vertically extending portions 22 of each of the pair of drop limiting members 20 are arranged outside the stored article Ws in the first direction X so as not to overlap with the stored article Ws when viewed in the second direction Y. However, the present invention is not limited to this. For example, the supported portion 21 of each of the pair of drop limiting members 20 may not move in the first direction X. Furthermore, in the release position P0, the vertically extending portions 22 of the pair of drop limiting members 20 may overlap with the stored article Ws when viewed in the second direction Y. Such an example is shown in FIG. 10 . In FIG. 10 , the drive mechanism 30 includes a pair of rotating bodies 36 that rotate about an axis r1 along the second direction Y. The pair of rotating bodies 36 are arranged spaced apart in the first direction X. Each of the pair of rotating bodies 36 supports the pair of supported portions 21 of each of the pair of drop-limiting members 20. In other words, the rotating bodies 36 serve as support portions 41 for supporting the supported portions 21. Furthermore, driven by the drop-limiting drive motor M6, the pair of rotating bodies 36 rotate in opposite directions about the axis r1 via the transmission mechanism 37 (simplified in FIG. 10 ). This causes each of the pair of drop-limiting members 20 to rotate about the axis r1, moving to the release position P0 and the restriction position P1. In the illustrated example, at the release position P0, the pair of vertically extending portions 22 of each of the pair of drop preventing members 20 do not overlap with any of the stored article Ws, the holding portion 6, the lifting portion 7, or the sliding portion 8 when viewed in the second direction Y. However, at the release position P0, the pair of vertically extending portions 22 of each of the pair of drop preventing members 20 may also overlap with the stored article Ws when viewed in the second direction Y. For example, such a configuration may be employed when the article transport vehicle 1 does not include the sliding portion 8. (4) In the above embodiment, the drive mechanism 30 is described as an example of a configuration of the drive unit 35, in which the drive mechanism 30 includes a plurality of pulleys 35b supported by the cover connection portion 53, a drive belt member 35a wound around the plurality of pulleys 35b and connected to the linear guide mechanism 31, and a drop-limiting drive motor M6 that rotates the pulleys 35b to drive the drive belt member 35a. However, the present invention is not limited to this. For example, the drive mechanism 30 may also include a ball screw 36a, a nut portion 36b screwed into the ball screw 36a, and a linkage shaft 36c connecting the nut portion 36b and a pair of support portions 41 (here, the moving body 31b) of the linear guide mechanism 31. Such an example is shown in FIG11. In the example of FIG11, the ball screw 36a is connected to the drop-limiting drive motor M6 and is arranged along the first direction X. Furthermore, the ball screw 36a is driven to rotate about its axis by the drop-limiting drive motor M6. In the illustrated example, male screws are formed on one side and the other side of the central portion of the ball screw 36a relative to the first direction X (travel direction), with the spirals oriented in opposite directions. Furthermore, the nut portions 36b are screwed into portions of the male screws in the ball screw 36a that are oriented in opposite directions. In other words, the nut portions 36b are arranged in a pair, separated in the first direction X. Furthermore, the interlocking shafts 36c are also arranged in a pair, separated in the first direction X. Furthermore, each interlocking shaft 36c is connected to a pair of movable bodies 31b of the direct-acting guide mechanism 31, and to the nut portions 36b, which face each other in the second direction Y. Therefore, when the ball screw 36a rotates in the first direction, the pair of nut portions 36b approach each other, and when the ball screw 36a rotates in the second direction, which is opposite to the first direction, the pair of nut portions 36b separate from each other. The pair of drop-restricting members 20 are linked to the movement of the pair of nut portions 36b toward and away from each other. Furthermore, the driving mechanism 30 may also include a rack and pinion mechanism as the driving portion 35, and the rack and pinion mechanism may be used to move the pair of drop-restricting members 20 in the first direction X. (5) In the above embodiment, the driving mechanism 30 is used as an example to explain the configuration in which the pair of drop-limiting members 20 are moved to a single limiting position P1 and a single release position P0. However, the configuration is not limited to this. For example, the limiting position P1 may be set to a plurality of positions in the first direction X. In this case, the driving mechanism 30 can move the pair of drop-limiting members 20 to a plurality of limiting positions P1 and a release position P0. Such an example is shown in FIG9 . In the example of FIG9 , a plurality of (here, two) limiting positions P1 are set in accordance with the size of the stored article Ws. More specifically, a plurality of limiting positions P1 are set in accordance with the width of the stored article Ws in the first direction X. In the illustrated example, when the size of the stored article Ws is large, the control device H moves the pair of drop-limiting members 20 to a position close to the release position P0, i.e., the large article limiting position P11. Furthermore, when the size of the stored articles Ws is small, the control device H moves the pair of drop prevention members 20 to the small article prevention position P12 set further inward of the large article prevention position P11 in the first direction X. In the illustrated example, two prevention positions P1 are set, but more than two prevention positions P1 may be set. (6) In the above embodiment, the vehicle body 5 is arranged below the running section 4. However, the present invention is not limited to this configuration. For example, the vehicle body 5 may be arranged above the running section 4. (7) In the above embodiment, the first direction X is a direction along the traveling direction of the traveling portion 4 as an example for explanation. However, the present invention is not limited to such a structure. For example, the first direction X may be a direction perpendicular to the traveling direction of the traveling portion 4 in the vertical direction. In this case, it is preferable that the second direction Y is a direction along the traveling direction of the traveling portion, and the article transport vehicle 1 travels along the second direction Y. Furthermore, for example, both the first direction X and the second direction Y may be directions inclined relative to the traveling direction of the traveling portion 4. [Overview of the above embodiment] The following is an overview of the article transport vehicle described above. The article transport vehicle disclosed herein is used for transporting articles and comprises: a traveling portion having wheels; a vehicle body connected to the traveling portion and forming a storage space for storing the articles; a holding portion for holding the articles in a suspended state; a lifting portion for lifting and lowering the holding portion relative to the vehicle body, so that the articles held by the holding portion are lifted and moved to a storage position within the storage space and a lowered position below the storage space; and a fall limiting device for limiting the fall of the articles, i.e., the stored articles, located at the storage position, Taking a specific direction in the horizontal direction as a first direction, a direction perpendicular to the first direction in a vertical direction perspective as a second direction, one side of the first direction as a first side of the first direction, and the other side of the first direction as a second side of the first direction, the vehicle body comprises: a first cover portion for covering the first side of the first direction relative to the storage space; The second cover portion covers the second side in the first direction relative to the aforementioned storage space; and a cover connecting portion connects the first cover portion and the second cover portion at the upper side relative to the aforementioned storage space, the aforementioned fall limiting device includes a pair of fall limiting members and a driving mechanism for driving the pair of the aforementioned fall limiting members, each of the pair of the aforementioned fall limiting members includes: a supported portion supported by the aforementioned cover connecting portion; a pair of vertical extension portions arranged to be separated from each other on both sides of the aforementioned storage article in the aforementioned second direction and extending downward from the aforementioned supported portion; and a lower side connecting portion connecting the pair of the aforementioned vertical extension portions at a lower side than the aforementioned storage article, the aforementioned driving mechanism drives the pair of the aforementioned fall limiting members to move them to a restricted position and a released position, in the aforementioned restricted position, the pair of the aforementioned vertical extension portions of each of the pair of the aforementioned fall limiting members overlap with the aforementioned storage article in a second direction viewing angle along the aforementioned second direction, and the aforementioned lower side connecting portion of each of the pair of the aforementioned fall limiting members is arranged to overlap with the aforementioned storage article in a vertical direction viewing angle, In the released position, the lower connecting portion of each of the pair of drop preventing members is arranged outside the stored article in the first direction so as not to overlap with the stored article when viewed in the vertical direction. According to this structure, the supported portion of each of the pair of drop limiting members is supported by the upper cover connecting portion relative to the storage space in the vehicle body. Moreover, by a pair of vertical extensions extending downward from the supported portion, the lower connecting portion, which is lower than the stored item, is supported in a suspended state. Therefore, when the pair of drop limiting members are in the restricted position, even if the retention of the item by the retaining portion is unintentionally released, the item can be supported by the lower connecting portion of each of the pair of drop limiting members. Therefore, it is possible to avoid the item falling from the pair of drop limiting members. In addition, when the item is supported by the lower connecting portion, the load of the item acts as a tensile load in the vertical direction. The tensile load is a tensile load on the drop limiting member that is in a vertical position from the supported portion to the lower connecting portion. That is, it is possible to avoid a large bending moment acting on the drop limiting member and the supporting portion supporting the drop limiting member. Therefore, even when the weight of the article is large, the rigidity of the drop-limiting member and the support portion does not need to be greatly increased, and the strength required to support the article can be easily ensured. In addition, it is easy to seek miniaturization or lightweighting of the drop-limiting member and the support portion. In addition, according to this structure, when the pair of drop-limiting members are in the restricted position, each vertical extension portion is configured to overlap with the accommodated article when viewed from the second direction. Therefore, it is also possible to prevent the article or a part thereof from falling off in the second direction. In this way, according to this structure, an article transport vehicle can be realized that has a drop-limiting device with a structure that can easily ensure strength regardless of the weight of the article. Here, it is preferable that the vehicle body is shaped so that at least one side in the second direction is open to the storage space, and the driving mechanism moves the supported portion of each of the pair of drop-limiting members toward the first direction. In the release position, the pair of vertically extending portions of each of the pair of drop-limiting members are arranged on the outside of the storage article in the first direction in a manner that does not overlap with the storage article when viewed from the second direction. According to this configuration, when the pair of drop-restricting members are in the restricting position, the pair of vertically extending portions of each of the drop-restricting members prevent the article or a portion thereof from falling in the second direction. When the pair of drop-restricting members are in the releasing position, the article can be moved from the storage position in the second direction. Therefore, for example, the article can be removed in the second direction and then transferred by sliding in the second direction. Furthermore, it is preferable that the driving mechanism includes: a guide portion that guides the supported portion of each of the pair of fall-limiting members to be movable toward the first direction; and a driving portion that moves the pair of supported portions toward opposite sides opposite to each other in the first direction. According to this configuration, the pair of drop-restricting members can be driven toward opposite sides in the first direction to appropriately move between the restricted position and the released position. Furthermore, in the released position, since the pair of drop-restricting members are spaced apart from each other on the outer sides of the stored articles in the first direction, it is easier to ensure a retraction space for the pair of drop-restricting members in the released position than in a configuration in which the pair of drop-restricting members are concentrated on either side of the stored articles in the first direction. Furthermore, it is preferable that the aforementioned limiting position can be set at a plurality of positions in the aforementioned first direction. According to this structure, since multiple limit positions can be set according to the size of the stored items, even if there are multiple sizes of items and the retention of the items by the retaining portion is unintentionally released, the items can be appropriately supported and prevented from falling. Furthermore, it is preferable that the vehicle body is arranged below the running section, and the cover connecting portion is connected to the running section. According to this structure, the supported portion of each of the pair of fall prevention members is supported by the cover connection portion, which is the connection portion with the running portion in the vehicle body. Therefore, the strength of the support portion for supporting the pair of fall prevention members can be easily ensured on the vehicle body side. Furthermore, it is preferable that the first direction is a direction along the traveling direction of the traveling portion. According to this configuration, even when a load caused by acceleration or deceleration of the traveling portion acts on the stored articles, the first cover portion and the second cover portion can prevent the articles or a portion thereof from falling out in the traveling direction (first direction). The article transport vehicle disclosed herein only needs to be able to achieve at least one of the above-mentioned effects. 1: Article Transport Vehicle 2: Fall Limiting Device 3: Travel Path 4: Traveling Unit 4a: Wheel 4d: Connecting Body 5: Vehicle Body 6: Holding Unit 6a: Gripping Claw 6b: Component 7: Lifting Unit 7a: Pulley 7b: Belt Component 8: Sliding Unit 8a: Sliding Body 9: Component 9a: Component 10: Processing Device 10a: Port 11: Command Acquisition Unit 20: Fall Limiting Component 21: Supported Unit 22: Vertical Extension 23: Belt Component Support 24: Lower Connecting Unit 30: Driving Mechanism 31: Direct-Acting Guide Mechanism 31a: Guide 31b: Moving Unit 32: Guide 35: Driving Unit 35a: Driving Belt Component 35b: Pulley 35c: Transmission Mechanism 36: Rotating Unit 36a: Ball Screw 36b: Nut 36c: Interlocking Shaft 37: Transmission Mechanism 41 : Support part 51: First cover part 52: Second cover part 53: Cover connecting part 60: Swing prevention mechanism 60a: Swing prevention body 60b: Swing prevention body support part 100: Article conveying equipment H: Control device IV-IV: Section line M1: Traveling motor M2: Holding motor M3: Lifting motor M4: Sliding motor M5: Rotation motor M6: Drop limiting drive motor P0: Release position P1: Limit position P11: Large article limiting position P12: Small article limiting position R: Track r1: Axis center S: Storage space T1: Storage position T2: Lowering position VV: Section line W: Article Wa: Held part Wb: Article body Ws: Article X: First direction X1: First direction first side X2: First direction second side Y: Second direction Figure 1 is a side view of an article transporting device. Figure 2 is a side view of an article transporting vehicle. Figure 3 is a top view schematically showing a driving mechanism of a drop limiting device. Figure 4 is a side view schematically showing a driving mechanism of a drop limiting device (IV-IV sectional view in Figure 3). Figure 5 is a front view schematically showing a driving mechanism of a drop limiting device (VV sectional view in Figure 4). Figure 6 is a top view schematically showing a main body and a lower connecting portion of a pair of drop limiting members. Figure 7 is a control block diagram. Figure 8 is a side view of an article transporting vehicle in another embodiment. Figure 9 is a side view of an article transporting vehicle in another embodiment. Figure 10 is a side view of an article transporting vehicle in another embodiment. Figure 11 is a top view schematically showing a driving mechanism of a drop limiting device in another embodiment. 1: Goods transport vehicle 2: Fall restriction device 3: Walking path 4: Walking part 4a: Wheel 4d: Connector 5: Car body 6: Maintaining part 6a: Gripping claw 6b: Component 7: Lifting part 7a: Pulley 7b: With components 8: Sliding part 8a: Sliding body 9: Component 9a: Component 20: Falling restriction member 22: Up and down extension 30: Driving mechanism 31: Direct-acting guide mechanism 31b: Mobile 32: Guide 35: Drive unit 35a: driving belt member 35b: Pulley 51: 1st cover 52: Second cover 53: Cover connection part M1: Travel motor M6: drop limit drive motor P0: Release position P1: Restricted position R: Track S: Containment Space T1: Containment Location W: Item Wa: maintained part Wb: Item body Ws: Item X: 1st direction X1: 1st direction, 1st side X2: 1st direction, 2nd side

Claims

1. An article transport vehicle for transporting articles, the article transport vehicle having the following features: comprising: a running gear having wheels; a vehicle body connected to the running gear and forming a receiving space for receiving the articles; a holding part for holding the articles in a suspended state; a lifting part for lifting the holding part relative to the vehicle body, for lifting the articles held in the holding part to a receiving position within the receiving space and a lower position below the receiving space; and a drop limiting device for limiting the drop of the articles located at the receiving position, wherein a specific direction in the horizontal direction is designated as a first direction, a direction perpendicular to the first direction in the vertical direction is designated as a second direction, one side of the first direction is designated as a first side of the first direction, and the other side of the first direction is designated as a second side of the first direction, the vehicle body comprising: a first cover covering the first side of the first direction relative to the receiving space; The second cover portion covers the second side of the first direction relative to the aforementioned receiving space; and the cover connecting portion connects the first cover portion and the second cover portion on the upper side relative to the aforementioned receiving space. The aforementioned drop restriction device includes a pair of drop restriction members and a drive mechanism for driving the pair of aforementioned drop restriction members. Each of the pair of aforementioned drop restriction members includes: a supported portion supported by the aforementioned cover connecting portion; a pair of vertically extending portions disposed on both sides of the aforementioned received item in the aforementioned second direction and extending downward from the aforementioned supported portion; and a lower connecting portion connected to the pair of aforementioned vertically extending portions on a side lower than the aforementioned received item. The aforementioned drive mechanism drives the pair of aforementioned drop restriction members to move them to a restricted position and a released position. In the restricted position, the pair of aforementioned vertically extending portions of each of the pair of aforementioned drop restriction members overlap with the aforementioned received item from a second-direction view along the aforementioned second direction, and the aforementioned lower connecting portion of each of the pair of aforementioned drop restriction members is configured to overlap with the aforementioned received item from a vertically extending view. In the aforementioned release position, the aforementioned lower connecting portion of each of the aforementioned pair of aforementioned drop limiting members is positioned on the outer side of the aforementioned first direction relative to the aforementioned contained item in a manner that does not overlap with the aforementioned contained item from a vertical perspective.

2. As in request item 1, the goods transport vehicle, wherein, The aforementioned vehicle body is in a shape that is open to the aforementioned containment space on at least one side of the aforementioned second direction. The aforementioned drive mechanism moves the aforementioned supported portion of each of the aforementioned pair of drop restraint members toward the aforementioned first direction. In the aforementioned released position, the pair of aforementioned vertical extensions of each of the aforementioned pair of drop restraint members are arranged on the outside of the aforementioned first direction relative to the aforementioned containment item in a manner that does not overlap with the aforementioned containment item from the perspective of the aforementioned second direction.

3. As in request item 2, the goods transport vehicle, wherein, The aforementioned drive mechanism includes: a guide portion for freely guiding the supported portion of each of the pair of aforementioned drop limiting members toward the aforementioned first direction; and a drive portion for moving the pair of aforementioned supported portions toward opposite sides that are opposite to the aforementioned first direction.

4. For any of the items requested in items 1 to 3, the transport vehicle, among which, The aforementioned limiting positions can be set in multiple positions in the aforementioned first direction.

5. For any of the items requested in items 1 to 3, the transport vehicle, among which, The aforementioned vehicle body is positioned below the aforementioned running gear, and the aforementioned cover connecting part is connected to the aforementioned running gear.

6. For any of the items requested in items 1 to 3, the transport vehicle, among which, The aforementioned first direction is the direction along the aforementioned walking direction of the walking part.

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