Overhead transport vehicle

Abstract

The present invention relates to an overhead transport vehicle capable of preventing articles from falling off from a container being transported by a simple mechanism without increasing the size of the device. The present invention is an overhead transport vehicle (1) for transporting a container (18) provided with an opening (24) for picking and placing an article (22) on the side thereof while the opening is kept open, the overhead transport vehicle (1) being characterized by comprising: a main body part (2); a gripping section (10) that grips a container in which an article is housed; a lifting unit (8) that lifts and lowers the grip unit relative to the main body unit; a drop prevention member (52) provided so as to face the opening of the container to be transported by the overhead transport vehicle, the drop prevention member (52) preventing the articles accommodated in the container from dropping from the opening; and a detection sensor (54) that detects whether or not the article is located below the fall prevention member.

Description

TECHNICAL FIELD

[0001] The present application relates to an overhead conveyor, and particularly to an overhead conveyor that conveys a container in which an article is accommodated while an opening of the container is kept in an open state. BACKGROUND

[0002] In Japanese Patent No. 5574177 (Patent Document 1), a conveyor is described. The conveyor is an overhead conveyor configured to convey an accommodation container in which a wafer is accommodated. The overhead conveyor is provided with a holding portion that holds the accommodation container to be conveyed, and the holding portion is configured to be able to be lifted by a wire. That is, the overhead conveyor is configured to lower the holding portion from above the accommodation container to be conveyed, and to pull up the accommodation container in a state where the accommodation container is held by the holding portion. Further, it is configured to convey the accommodation container in which the wafer is accommodated, in a state where the accommodation container is held by the holding portion, by traveling along a traveling rail laid on a ceiling.

[0003] Further, since the accommodation container is conveyed in an open state, the overhead conveyor is provided with a protrusion prevention mechanism in order to prevent the wafer from protruding from the accommodation container during conveyance. The protrusion prevention mechanism is provided to be able to be lifted together with the holding portion, and when the holding portion is lowered from above the accommodation container in order to hold the accommodation container, the protrusion prevention mechanism is retracted to a separation position where it does not interfere with the wafer accommodated in the accommodation container. Further, the protrusion prevention mechanism is configured to move to a contact position that opposes the opening portion of the accommodation container after the accommodation container is held by the lowered holding portion, and to prevent the wafer from protruding from the accommodation container during conveyance. In addition, in a case where the wafer is accommodated in a state of protruding from the accommodation container, the wafer is pressed into a proper position of the accommodation container by the action of the protrusion prevention mechanism.

[0004] PRIOR ART DOCUMENTS PATENT DOCUMENTS Patent Document 1: Japanese Patent No. 5574177 SUMMARY

[0005] PROBLEMS TO BE SOLVED BY THE INVENTION However, in the conveyor described in Patent Document 1, a mechanism is required to move the protrusion prevention mechanism between the separation position and the contact position, and thus there is a problem in that the configuration of the conveyor becomes complicated. In addition, in the conveyor described in Patent Document 1, the protrusion prevention mechanism needs to be retracted by a large amount so that the protrusion prevention mechanism in the separation position does not come into contact with the wafer even in a state where the wafer protrudes from the accommodation container. Therefore, the protrusion prevention mechanism requires a large stroke for moving from the separation position to the contact position, and there is a problem in that the entire conveyor becomes large.

[0006] Therefore, an object of the present application is to provide a high-level transport vehicle capable of preventing articles from falling out of a container in transport by a simple mechanism without increasing the size of the device.

[0007] Means for solving the problem To solve the above problem, the present application is a high-level transport vehicle that transports a container having an opening for taking in and out articles provided on the side, characterized by having: a main body portion; a holding portion that holds the container in which the articles are stored; a lifting portion that lifts the holding portion with respect to the main body portion; a falling prevention member that is provided in opposition to the opening of the container to be transported by the high-level transport vehicle, and prevents the articles stored in the container from falling out of the opening; and a detection sensor that detects whether the articles are positioned below the falling prevention member.

[0008] According to the present application thus configured, since the falling prevention member is provided in opposition to the opening of the container to be transported, it is possible to prevent the articles from falling out of the container in transport. Furthermore, according to the present application thus configured, whether the articles are positioned below the falling prevention member is detected by the detection sensor. Therefore, when the container is received by the high-level transport vehicle, it is possible to detect a positional deviation of the articles stored in the container. As a result, even if a mechanism for retraction of the falling prevention member is not provided, it is possible to cope with the positional deviation of the articles, it is possible to prevent the articles from falling out by a simple mechanism, and it is possible to downsize the device.

[0009] In the present application, it is preferable that the falling prevention member is composed of a plurality of members extending in the vertical direction in opposition to the opening of the container to be transported.

[0010] According to the present application thus configured, the falling prevention member is composed of a plurality of members extending in the vertical direction in opposition to the opening of the container to be transported, and thus it is possible to reliably prevent the articles from protruding out of the container.

[0011] In the present application, it is preferable that the detection sensor is configured to detect whether the articles are in contact with the lower end of the falling prevention member.

[0012] According to the present application thus configured, the detection sensor detects whether the articles are in contact with the lower end of the falling prevention member, and thus it is possible to reliably detect the interference of the falling prevention member with the articles.

[0013] In the present application, it is preferable that the detection sensor is a contact sensor provided at the lower end of the falling prevention member.

[0014] According to the present application thus configured, the detection sensor is composed of the contact sensor provided at the lower end of the falling prevention member, and thus it is possible to reliably detect the interference of the falling prevention member with the articles by a simple mechanism, a sensor.

[0015] It is preferable in the present application that the detection sensor is a proximity sensor, a photoelectric sensor, or a laser sensor that detects the article.

[0016] According to the present application thus configured, since the detection sensor is configured by a proximity sensor, a photoelectric sensor, or a laser sensor that detects the article, it is possible to detect the article protruding from the container before the drop preventing member interferes with the article, and it is possible to avoid damage to the article.

[0017] It is preferable in the present application that the lift section is stopped when the article is detected by the detection sensor.

[0018] According to the present application thus configured, the lift section is stopped when the article is detected by the detection sensor, and therefore it is possible to reduce the risk of the article being damaged even in the case where the drop preventing member comes into contact with the article.

[0019] Effects of the Invention According to the overhead conveyor of the present application, it is possible to prevent the article from dropping from the container in the conveyance by a simple mechanism without making the device large. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a side view showing the schematic configuration of the overhead conveyor as a whole of the embodiment of the present application.

[0021] Figure 2 is a perspective view showing the schematic configuration of the holding device provided in the overhead conveyor of the embodiment of the present application.

[0022] Figure 3 is a sectional view of the overhead conveyor of the embodiment of the present application taken along the line III-III of Figure 1

[0023] Figure 4 is a view showing the action of the overhead conveyor of the embodiment of the present application, and shows the case where each wafer is properly housed in the open cassette.

[0024] Figure 5 is a view showing the action of the overhead conveyor of the embodiment of the present application, and shows the case where the wafer protrudes from the open cassette.

[0025] Figure 6 is a view showing a modification example of the drop preventing member and the contact sensor in the overhead conveyor of the embodiment of the present application.

[0026] Figure 7 is a view showing the action of the overhead conveyor of the modification example of the embodiment of the present application. DETAILED DESCRIPTION

[0027] Next, the overhead conveyor of the embodiment of the present application will be described with reference to the drawings.​

[0028] First, referring to Figure 1 The overall configuration of the overhead transport vehicle of the embodiment of the present application will be described. Figure 1 is a side view showing the overall configuration of the overhead transport vehicle of the embodiment of the present application. Further, the embodiment to be described below is a transport device to which the present application is applied to house and transport semiconductor wafers in a clean room of a semiconductor manufacturing plant.

[0029] First, as Figure 1 indicated, the overhead transport vehicle 1 of the embodiment has a dolly main body 2 as a main body portion, which is suspended from a rail guide 4 installed on a ceiling of a building such as a clean room, and moves to a position as a target by traveling through a traveling mechanism 6 that acts with respect to the rail guide 4.

[0030] Next, the overhead transport vehicle 1 has a lifting device 8 as a lifting portion and a holding device 10 as a holding portion.

[0031] The lifting device 8 is a device that lifts the holding device 10 with respect to the dolly main body 2 by a pair of lifting belts 12, 14 that function as so-called hoists, and is installed to the dolly main body 2 at a position below the traveling mechanism 6.

[0032] The holding device 10 is used to hold (retain) a container, i.e., an open box 18, placed on a load port 16 of a semiconductor manufacturing device provided to a building by a chuck 20, and can transport an article, i.e., a wafer 22, in the open box 18.

[0033] The open box 18 is formed with an opening 24 in one side surface thereof, and the wafer 22 of the load port 16 is horizontally transferred into the open box 18 from the opening 24 (the wafer 22 is taken out through the opening 24).

[0034] Here, a configuration in which a horizontal position at which the wafer 22 is held is not provided on the open box 18. Generally, since a large force in the horizontal direction is not applied to the wafer 22, the open box 18 is transported by the overhead transport vehicle 1 in a state in which the opening 24 is kept open. However, during traveling, the wafer 22 can be moved due to centrifugal force at a curve, traveling vibration, or the like. Therefore, in the embodiment, as will be described later, a falling prevention member 52 (see FIG. 6) is provided in opposition to the opening 24 provided to the side of the open box 18, and the wafer 22 housed in the open box 18 is prevented from falling out of the opening 24. Figure 2

[0035] As Figure 1 indicated, the lifting device 8 has a first lifting belt 12 (only one is illustrated in Figure 1 ) consisting of a pair of belts, a pair of lifting rollers 26, and a pair of idlers 28 (only one is illustrated in Figure 1 ​(Only one is shown in the figure). The first lifting belt 12 is mounted at the beginning of the lifting drum 26. The first lifting belt 12 is wound up or unwound via the idler wheel 28 by rotating the lifting drum 26.

[0036] Additionally, the lifting device 8 includes a second lifting belt 14 composed of a single belt, a lifting roller 30 disposed between a pair of lifting rollers 26 for the second lifting belt, and two idler pulleys 32. The starting end of the second lifting belt 14 is mounted on the lifting roller 30, and the second lifting belt 14 is wound up or unwound via the two idler pulleys 32 by rotating the lifting roller 30.

[0037] Here, a total of three lifting rollers 26 and 30 are driven by a common drive shaft (not shown) connected to a motor (not shown), thereby all being driven at the same speed and the same amount of rotation. Furthermore, all three lifting rollers 26 and 30 have the same diameter. Therefore, with this configuration, when the lifting rollers 26 and 30 are rotated, the first lifting belt 12 and the second lifting belt 14 are wound up or unwound by the same length.

[0038] Next, as Figure 1 As shown, the lower end of the first lifting belt 12 is mounted on the retaining device 10 at the opening 24 side of the open box 18, and the lower end of the second lifting belt 14 is mounted on the retaining device 10 at the back side of the open box 18. That is, the first lifting belt 12 suspends the retaining device 10 at the opening 24 side of the open box 18, and the second lifting belt 14 suspends the retaining device 10 at the back side of the retaining device 10.

[0039] Next, refer to Figure 2 and Figure 3 Explain the basic structure of the holding device 10.

[0040] Figure 2 This is a perspective view showing the schematic configuration of the holding device 10 provided by the elevated transport vehicle 1 according to an embodiment of the present invention. Figure 3 It is along Figure 1 A sectional view along line III-III. Furthermore... Figure 2 This indicates that the holding device 10 has descended to the position where the open box 18 is held by the chuck 20.

[0041] First, such as Figure 2 As shown, the holding device 10 includes a base plate 50 capable of mounting various parts. A pair of first lifting belts 12 are mounted on the upper surface of the base plate 50 via a pair of first connecting members 36. Furthermore, a second lifting belt 14 is mounted on the upper surface of the base plate 50 via a second connecting member 40.

[0042] On the other hand, a pair of chucks 20 for holding the open box 18 are provided on the lower surface of the base plate 50. Figure 2Only one of the chucks 20 is illustrated. These chucks 20 are configured to be able to slide in the lateral direction on the lower side of the base plate 50. That is, each chuck 20 has: an engagement member 20a that extends downward from the base plate 50 and engages with the open case 18; a sliding member 20b that extends in the horizontal direction on the lower side of the base plate 50; and a drive motor 20c that moves each sliding member 20b.

[0043] The engagement member 20a is a member that is installed in a manner that protrudes downward from one end of the sliding member 20b, and is configured so that the lower end portion is able to engage with the upper portion of the open case 18. The sliding member 20b is an elongated member that is installed on the lower side of the base plate 50, and is configured to slide along the base plate 50 by the drive motor 20c. By this configuration, as shown in Figure 2 after the holding device 10 is lowered above the open case 18, when the sliding members 20b are caused to slide by the drive motor 20c to bring the respective engagement members 20a closer to each other, the engagement members 20a engage with the upper portion of the open case 18 and the open case 18 is held by the holding device 10.

[0044] Further, two drop prevention members 52 are installed on the base plate 50 in a manner that extend downward in the vertical direction. These drop prevention members 52 are rod-shaped members that extend in the vertical direction in a manner that oppose the opening 24 of the open case 18 that is held by the holding device 10. That is, as shown in Figure 3 the two drop prevention members 52 are arranged in a manner that oppose the opening 24 of the open case 18 and extend in the vertical direction, and prevent the wafer 22 from dropping from the open case 18 during conveyance of the open case 18.

[0045] In addition, as shown in Figure 3 in the state where the chuck 20 of the holding device 10 holds the open case 18, the wafer 22 that is properly housed in the open case 18 is separated from each drop prevention member 52 when viewed from above, and the wafer 22 does not come into contact with the drop prevention member 52. However, as shown by the imaginary line in Figure 3 when the wafer 22 protrudes from the open case 18 without being housed in the proper position, when the holding device 10 is lowered in order to hold the open case 18, the lower end of the drop prevention member 52 sometimes comes into contact with the wafer 22.

[0046] Here, a contact sensor 54, serving as a detection sensor, is installed at the lower end of each drop prevention component 52. The front end 54a of the lower end of these contact sensors 54 is bent at an angle toward the wafer 22 housed in the open box 18. Each contact sensor 54 is configured to detect when an object comes into contact with its front end 54a. Furthermore, the front end 54a of the contact sensor 54 extends closer to the opening 24 of the open box 18 than the outer peripheral surface of the drop prevention component 52. Therefore, when the holding device 10 is lowered, if the front end 54a of the contact sensor 54 does not come into contact with the wafer 22, the drop prevention component 52 will not come into contact with the wafer 22. That is, the contact sensor 54 is configured to detect whether an object (wafer 22) is below the drop prevention component 52 by detecting whether the object (wafer 22) is in contact with the lower end of the drop prevention component 52.

[0047] Furthermore, the detection signal from the contact sensor 54 is sent to a control unit (not shown) provided in the trolley body 2. When the contact sensor 54 detects an object (chip 22), the control unit sends a control signal to the lifting device 8, stopping the rising or falling of the holding device 10 based on the lifting device 8. Additionally, the control unit is configured to emit a warning sound via a sounder (not shown) provided in the trolley body 2 when the contact sensor 54 detects an object, reporting the contact between the chip 22 and the contact sensor 54. Furthermore, the invention can also be configured to illuminate a warning light reporting contact, either along with or in place of the warning sound.

[0048] Next, refer to Figure 4 and Figure 5 The function of the elevated transport vehicle 1 in the embodiments of the present invention will be explained.

[0049] Figure 4 This diagram illustrates the function of the overhead conveyor 1 when each wafer 22 is properly housed in the open box 18. Figure 5 This diagram illustrates the function of the overhead conveyor 1 when the wafer 22 protrudes from the open box 18.

[0050] First, such as Figure 4 As shown in column (a), when the open box 18 positioned on the loading port 16 is being transported by the overhead conveyor 1, the overhead conveyor 1 is moved along the guide rail 4 to directly above the open box 18 to be transported and then stopped. In this state, the lifting device 8 ( Figure 1 The device operates to lower the holding device 10.

[0051] Next, as Figure 4As shown in column (b), when the holding device 10 descends to a predetermined position above the open box 18, the lifting device 8 stops the descent of the holding device 10. At this time, since each wafer 22 is housed in the appropriate position in the open box 18, the front end 54a of the lower end of the drop prevention component 52 will not contact the wafer 22. Next, the drive motor 20c of the holding device 10 ( Figure 2 When the chuck 20 is in operation, the engaging parts 20a of the chuck 20 move toward each other. As a result, the open box 18 is held by the chuck 20 of the holding device 10.

[0052] When the open box 18 is held by the holding device 10, such as Figure 4 As shown in column (c), the lifting device 8 operates, and the open box 18 is pulled upward from the loading port 16. When the open box 18 is pulled to the designated position, the lifting device 8 stops. Then, with the open box 18 suspended, the traveling mechanism 6 of the overhead conveyor 1 operates, and the overhead conveyor 1 travels along the guide rail 4 to the intended transport destination. At this time, the wafer 22 is prevented from falling out of the open box 18 by the drop prevention component 52 located opposite the opening 24 of the open box 18.

[0053] Next, refer to Figure 5 This explains the function of the overhead conveyor 1 when the wafer 22 protrudes from the open box 18.

[0054] First, such as Figure 5 As shown in column (a), in order to transport the open box 18 configured on the loading port 16, the lifting device 8 ( Figure 1 The device operates to lower the holding device 10.

[0055] Then, as Figure 5 As shown in column (b), when the wafer 22 protrudes from the open box 18, the front end 54a of the lower end of the drop prevention member 52 contacts the protruding wafer 22 before the holding device 10 descends to a predetermined position above the open box 18. This contact is detected by a contact sensor 54 located at the lower end of the drop prevention member 52. The detection signal from the contact sensor 54 is sent to the control unit (not shown) of the trolley body 2 of the overhead conveyor 1. When contact is detected by the contact sensor 54, the control unit stops the lifting device 8, halting the descent of the holding device 10.

[0056] In addition, the control unit generates a warning sound via a speaker (not shown) and flashes a warning light (not shown) to report an abnormality to the operator. When the alarm is triggered, the operator confirms the abnormal status of the overhead conveyor 1 and takes necessary measures. For example, the operator moves the protruding wafer 22 to the appropriate position in the open box 18, restarting the operation of the overhead conveyor 1. Alternatively, if the wafer 22 is damaged due to contact, the damaged wafer 22 is removed, and the operation of the overhead conveyor 1 is restarted after confirming that no fragments of the damaged wafer 22 remain.

[0057] Preferably, the descent of the holding device 10 is stopped immediately upon detection of contact, so that the wafer 22 is not damaged even if the front end 54a comes into contact with the wafer 22. Alternatively, the front end 54a can be formed of a soft material so that the wafer 22 is not damaged even if contact occurs.

[0058] The overhead conveyor 1 according to an embodiment of the present invention, having a drop prevention member 52 disposed opposite to the opening 24 of the open box 18 to be conveyed, can prevent the wafer 22 from falling off the open box 18 during conveying. Furthermore, the overhead conveyor 1 according to this embodiment detects whether the wafer 22 is located below the drop prevention member 52 using a contact sensor 54. Therefore, even without a mechanism to retract the drop prevention member 52, it is possible to handle positional deviations of the wafer 22 housed in the open box 18, prevent the wafer 22 from falling off with a simple mechanism, and enable miniaturization of the device.

[0059] Furthermore, according to the overhead conveyor 1 of this embodiment, the drop prevention component 52 is composed of a plurality of components that extend in the vertical direction in a manner opposite to the opening 24 of the open box 18 to be conveyed, thus reliably preventing the wafer 22 from protruding from the open box 18.

[0060] Furthermore, according to the elevated transport vehicle 1 of this embodiment, the contact sensor 54 detects whether the chip 22 is in contact with the lower end of the fall prevention component 52, thus reliably detecting the interference between the fall prevention component 52 and the chip 22.

[0061] Furthermore, according to this embodiment, the elevated transport vehicle 1 detects the wafer 22 by means of a contact sensor 54 provided at the lower end of the fall prevention component 52, thus enabling reliable detection of interference between the fall prevention component 52 and the wafer 22 through a simple mechanism and sensor.

[0062] Furthermore, according to the elevated transport vehicle 1 of this embodiment, when the contact sensor 54 detects the wafer 22, the lifting device 8 is stopped, so even if the fall prevention component 52 comes into contact with the wafer 22, the risk of damage to the wafer 22 can be reduced.

[0063] The embodiments of the present invention have been described above, but various modifications can be made to the above embodiments. In particular, in the above embodiments, the present invention is applied to an overhead conveyor 1 for transporting an open box 18 containing a wafer 22, but the present invention can also be applied to an overhead conveyor for transporting any container containing any item.

[0064] Furthermore, in the above embodiment, the front end 54a of the lower end of the contact sensor 54, which serves as a detection sensor, contacts the wafer 22 protruding from the open box 18. However, as a variation, the contact sensor can also be configured such that... Figure 6 That's how it's structured. In Figure 6 In the modified example shown, a circular contact plate 58a is mounted on the lower end of a contact sensor 58 located at the lower end of the drop prevention member 56. Each contact sensor 58 is configured to detect when an object comes into contact with the contact plate 58a mounted on the lower end. Furthermore, the diameter of the contact plate 58a of the contact sensor 58 is configured to be larger than the outer diameter of the drop prevention member 56. Therefore, when the holding device 10 is lowered, if the contact plate 58a does not contact the wafer 22, the drop prevention member 56 will not contact the wafer 22. According to this configuration, when the wafer 22 protrudes from the open box 18 to a position where it interferes with the drop prevention member 56, the protruding wafer 22 first contacts the contact plate 58a of the contact sensor 58. Therefore, it is possible to detect whether an object is located below the drop prevention member by means of the contact sensor 58.

[0065] Furthermore, in the above embodiment, the contact sensor is disposed at the lower end of the drop prevention member, but the contact sensor can also be disposed at other locations. For example, the drop prevention member can be configured to slide vertically, and when it comes into contact with the wafer, the drop prevention member moves upward. Moreover, the present invention can also be configured to detect the upward sliding of the drop prevention member by means of a contact sensor disposed at the upper end of the drop prevention member.

[0066] Furthermore, in the above embodiment, a contact sensor is used to detect the protruding chip; however, as a variation, a proximity sensor, photoelectric sensor, or laser sensor that detects objects in a non-contact manner can also be used as the detection sensor. In this case, such as Figure 7As shown, a proximity sensor 62 is mounted on the lower end of the fall prevention component 60. Then, when the wafer 22 approaches within a predetermined distance L below the proximity sensor 62, the proximity sensor 62 detects the wafer 22. When the wafer 22 is detected below the proximity sensor 62, the control unit (not shown) sends a control signal to the lifting device 8 to stop the descent of the holding device 10. According to this modification, a protruding wafer 22 can be detected before the detection sensor contacts the wafer 22. Therefore, the descent of the holding device 10 can be stopped before the proximity sensor 62 contacts the wafer 22, reliably preventing damage to the wafer 22.

[0067] Furthermore, in the above embodiment, the drop prevention component is installed on the holding device 10, and when the holding device 10 is lowered to hold the open box 18, the protruding chip 22 is detected to be in contact with or approaching the detection sensor. In contrast, as a variation, a drop prevention component can also be provided on the side of the trolley body 2. In this case, when the open box 18 is pulled up to the trolley body 2, the drop prevention component faces the opening 24 of the open box 18. Therefore, in this variation, the protruding chip 22 is detected by the detection sensor while the open box 18 is held by the holding device 10 and pulled up by the lifting device 8.

[0068] Explanation of symbols 1: Overhead conveyor; 2: Cart body (main body); 4: Track guide rail; 6: Traveling mechanism; 8: Lifting device (lifting part); 10: Holding device (holding part); 12, 14: Lifting belt; 16: Loading port; 18: Open box (container); 20: Chuck; 20a: Engaging component; 20b: Sliding component; 20c: Drive motor; 22: Chip (item); 24: Opening; 26: Lifting roller; 28: Idler wheel; 30: Lifting roller; 32: Idler wheel; 36: First connecting component; 40: Second connecting component; 50: Base plate; 52: Fall prevention component; 54: Contact sensor (detection sensor); 54a: Front end; 56: Fall prevention component; 58: Contact sensor (detection sensor); 58a: Contact plate; 60: Fall prevention component; 62: Proximity sensor (detection sensor)

Claims

1. An elevated conveyor vehicle for conveying a container with an opening on its side for picking up and placing items, wherein the opening is kept open, characterized in that, Having: a main body section; a holding section that holds a container that holds an article; a lifting section that lifts the holding section with respect to the main body section; a falling prevention member that is provided in opposition to an opening of a container that should be transported by the overhead transport vehicle, and that prevents an article held in the container from falling from the opening; and a detection sensor that detects whether an article is positioned below the falling prevention member.

2. The overhead transport vehicle according to claim 1, wherein the falling prevention member is composed of a plurality of members that extend in the up-and-down direction in opposition to the opening of the container that should be transported.

3. The overhead transport vehicle according to claim 1 or 2, wherein the detection sensor is configured to detect whether an article is in contact with a lower end of the falling prevention member.

4. The overhead transport vehicle according to claim 3, wherein the detection sensor is a contact sensor that is provided at the lower end of the falling prevention member.

5. The overhead transport vehicle according to claim 1 or 2, wherein the detection sensor is a proximity sensor, a photoelectric sensor, or a laser sensor that detects an article.

6. The overhead transport vehicle according to claim 1 or 2, wherein the lifting section is stopped when an article is detected by the detection sensor.

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