Patent Publication Number: US-2023134312-A1

Title: Gripper device, conveyance vehicle, and conveyance method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a gripper device that holds an article, a conveyance vehicle including the gripper device, and a conveyance method for holding and carrying the article. 
     2. Description of the Related Art 
     As described in Japanese Unexamined Patent Publication No. 2011-35022, an overhead conveyance vehicle system is known that transports an article, such as a front opening unified pod (FOUP), in a state of suspending the article. In this system, a flange provided on a top surface of the FOUP is gripped from both sides of the flange by an elevating platform. 
     SUMMARY OF THE INVENTION 
     In the above-described conventional system, a single flange is provided on the top surface of the article, and this flange is gripped by an elevating platform. A large gripper device is needed to grip the flange from both sides thereof. 
     Preferred embodiments of the present disclosure provide gripper devices, conveyance vehicles, and conveyance methods that are each able to hold an article in a compact configuration. 
     A preferred embodiment of the present disclosure provides a gripper device to hold an article including a pair of held portions that are provided on a top surface of the article and that are spaced apart in a direction along the top surface, the gripper device including a pair of engaging portions that are attached to an elevating section capable of lifting and lowering above the article and are respectively engageable with the pair of held portions, and a driver to move the pair of engaging portions along the above-described direction, from a standby position where a distance between the pair of engaging portions is less than an interval between the pair of held portions, to an engaging position where the pair of engaging portions is capable of engaging with the pair of held portions, such that the pair of engaging portions separate from one another. 
     According to this gripper device, the pair of engaging portions attached to the elevating section is able to be moved from the standby position to the engaging position by the driver. The top surface of the article is provided with the pair of held portions that are spaced apart in a predetermined direction. The pair of engaging portions are between (inside) the pair of held portions when the gripper device is to hold the article, and are moved from inside to outside of the article along the above-described predetermined direction. This arrangement of the engaging portions, and their movement and engagement in a single direction, make the gripper device compact as a whole. According to this gripper device, an article is able to be held in a compact configuration. 
     The gripper device may include a pair of drop preventing sections that are fixed to the elevating section and capable of being spaced apart in the direction with a longer interval than the interval between the pair of held portions. A first gap exists between each of the pair of drop preventing sections and each of the pair of engaging portions at the standby position, the first gap allowing each of the pair of held portions to vertically pass therethrough, and a second gap exists between each of the pair of drop preventing sections and each of the pair of engaging portions located at the engaging position, the second gap not allowing each of the pair of held portions to vertically pass therethrough. When the elevating section is lowered in a state where the pair of engaging portions are located at the standby position, the held portion passes through the first gap between the engaging portion and the drop preventing section in each of both end regions in the above-described direction. When the pair of engaging portions are moved to the engaging position and engage with the pair of held portions, in each of both end regions in the above-described direction, the held portion is not able to pass through the second gap between the engaging portion and the drop preventing section. Even if one of the held portions (or one of the engaging portions) is damaged due to some unforeseen event, for example, the other held portion is held and maintained between the other engaging portion and the drop preventing section. Thus, an engagement structure of either one of the engaging portions is able to be maintained, and the article is able to be prevented from dropping. 
     The article may be provided with at least a pair of columns on the top surface of the article and a pair of held portions fixed to the columns. Each of the pair of engaging portions may have a notch that accepts the column when the pair of engaging portions are located in the engaging position. According to this configuration, when the columns are provided, a space into which the engaging portion is inserted is able to be easily provided between the top surface of the article and the held portion. Furthermore, in the movement of the engaging portions in the above-described direction, it is possible to perform control, for example, to allow a portion of the engaging portion to come into contact with the column from the inside. In such a case, the engaging portions are able to be positioned securely and easily. 
     The driver may include a single link mechanism to move the pair of engaging portions. Since only one link mechanism is used to move the pair of engaging portions, the structure of the driver is simpler than when multiple link mechanisms are used. In addition, since one common link mechanism is provided for the pair of engaging portions, the operation of the pair of engaging portions is more easily synchronized. 
     According to another preferred embodiment of the present disclosure, there may be provided a conveyance vehicle that includes either of the above-described gripper devices and travels along a track provided on a ceiling. According to this conveyance vehicle, since the gripper device has the compact configuration described above, the conveyance vehicle is able to be made compact and lightweight relative to the article in the size, the weight, and the like. 
     A further preferred embodiment of the present disclosure provides a conveyance method for holding and carrying, with a gripper device, an article with a pair of held portions that are provided on a top surface of the article and spaced apart in a direction along the top surface, in which the gripper device includes a pair of engaging portions attached to an elevating section capable of lifting and lowering above the article and that respectively engage with the pair of held portions, the conveyance method including lowering the elevating section, moving the pair of engaging portions along a direction from a standby position where the distance between the pair of engaging portions is less than an interval between the pair of held portions to an engaging position where the pair of engaging portions is capable of engaging with the pair of held portions, and holding the article by causing the elevating section to lift and causing the pair of engaging portions in the engaging position to engage with the pair of held portions. 
     According to this conveyance method, the same actions and effects as described above are achieved. In other words, in the holding step, an article is able to be held in the compact configuration. The gripper device has the compact configuration, and is able to make use of the advantage of being compact and lightweight when carrying held an article. For example, this conveyance method is also advantageous in terms of providing faster carrying speeds and reducing power consumption. 
     According to preferred embodiments of the present disclosure, an article is able to be held in the compact configuration. 
     The above and other elements, features, steps, characteristics, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram illustrating an outline configuration of a conveyance vehicle including a gripper device according to a preferred embodiment of the present disclosure. 
         FIG.  2    is a plan view of the gripper device in  FIG.  1   . 
         FIG.  3    is a perspective view of an article to be carried by a conveyance vehicle system of  FIG.  1   . 
         FIG.  4    is a diagram of the gripper device viewed from a side, indicating a state where a pair of engaging portions are located in a standby position. 
         FIG.  5    is a diagram of the gripper device viewed from the side, indicating a state where the pair of engaging portions are located in an engaging position. 
         FIG.  6    is a plan view indicating a state where the engaging portion engages with the held portion. 
         FIG.  7    is a cross-sectional view along VII-VII line of  FIG.  6   . 
         FIG.  8    is an enlarged view of a portion of  FIG.  5   . 
         FIG.  9    is a diagram indicating a state where one of the held portions is held when the other of the held portions is damaged. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As illustrated in  FIG.  1   , an overhead conveyance vehicle (conveyance vehicle)  1  according to a preferred embodiment of the present invention travels along a track  100  laid on a ceiling  110  of a clean room where semiconductor devices are manufactured. The overhead conveyance vehicle  1  of the one embodiment carries front opening unified pod (FOUP) (article)  200  accommodating a plurality of semiconductor wafers, and transfers the FOUP  200  to a load port  300  or the like that is a transfer section provided in a processing device that performs various types of processing on the semiconductor wafers. The track  100  is suspended from the ceiling  110  by a suspension column  108 . The track  100  includes a traveling rail  101  and a feeder rail  102  that is provided at a lower portion of the traveling rail  101 . 
     The overhead conveyance vehicle  1  includes a frame unit  2 , a traveling unit  3   a,  a power receiving unit  3   b,  a lateral unit  4 , a theta unit  5 , an elevating drive unit  6 , a gripper device  10 , and a controller  8 . The frame unit  2  includes a center frame  21 , a front frame  22 , and a rear frame  23 . The front frame  22  extends downward from an end of a front side (front side in a travel direction of the overhead conveyance vehicle  1 ) in the center frame  21  to a lower side thereof. The rear frame  23  extends downward from an end of a rear side (rear side in the travel direction of the overhead conveyance vehicle  1 ) in the center frame  21  to the lower side thereof. 
     The traveling unit  3   a  and the power receiving unit  3   b  are disposed on the upper side of the center frame  21 . The traveling unit  3   a  is attached to the traveling rail  101 . The power receiving unit  3   b  receives, for example, power supply in a non-contact manner from a high-frequency current line laid along the feeder rail  102 . The power supply to the power receiving unit  3   b  causes the traveling unit  3   a  to travel along the track  100 . The lateral unit  4  is disposed on the lower side of the center frame  21 . The lateral unit  4  moves the theta unit  5 , the elevating drive unit  6 , and the gripper device  10  to move laterally (side in the travel direction of the overhead conveyance vehicle  1 ). The theta unit  5  is disposed on a lower side of the lateral unit  4 . The theta unit  5  rotates the elevating drive unit  6  and the gripper device  10  in a horizontal plane. 
     The elevating drive unit  6  is disposed on the lower side of the theta unit  5 . The elevating drive unit  6  lifts and lowers gripper device  10 . The gripper device  10  is disposed on the lower side of the elevating drive unit  6 . The gripper device  10  holds a flange section (held portion)  202  of the FOUP  200 . The controller  8  is disposed on the front frame  22  and the rear frame  23 . The controller  8  is an electronic control unit including a CPU, ROM, and RAM. The controller  8  controls each element or component of the overhead conveyance vehicle  1 . 
     To the front frame  22  and the rear frame  23 , four lower drop preventing sections  26  and two lid drop preventing sections  27  that each prevent the FOUP  200  from dropping from the frame unit  2  are attached. The lower drop preventing sections  26  are correspondingly attached to the lower end of the front frame  22  and the lower end of the rear frame  23  at the four corner positions of the frame unit  2  and correspondingly face the front end and the rear end of the bottom of the FOUP  200 . The lid drop preventing sections  27  are attached to the lower portion of the front frame  22  and the lower portion of the rear frame  23 , respectively, and face the FOUP  200  from the lid  205  side (see  FIG.  3   ). These lower drop preventing sections  26  and the lid drop preventing sections  27  are opened and closed at appropriate timing in association with transfer of the FOUP  200 . 
     The overhead conveyance vehicle  1  configured as described above operates, as an example, described below. When the FOUP  200  is transferred from a load port  300  to the overhead conveyance vehicle  1 , the overhead conveyance vehicle  1  that does not hold the FOUP  200  stops above the load port  300 . When a horizontal position of the gripper device  10  deviates from the position directly above the load port  300 , the horizontal position and an angle of a holding unit are fine-tuned by driving the lateral unit  4  and the theta unit  5  to fine-tune the whole elevating drive unit  6 . Subsequently, the elevating drive unit  6  lowers the gripper device  10 , and the gripper device  10  holds the flange section  202  of the FOUP  200  that is placed on the load port  300 . The elevating drive unit  6  then lifts the gripper device  10  to a lifting end and disposes the FOUP  200  between the front frame  22  and the rear frame  23 . The lower drop preventing sections  26  and the lid drop preventing sections  27  are closed. The overhead conveyance vehicle  1  holding the FOUP  200  then begins traveling. 
     When the FOUP  200  is transferred from the overhead conveyance vehicle  1  to the load port  300 , the overhead conveyance vehicle  1  holding the FOUP  200  stops above the load port  300 . The lower drop preventing section  26  and the lid drop preventing section  27  are opened. When the horizontal position of the gripper device  10  (FOUP  200 ) deviates from a position directly above the load port  300 , the horizontal position and the angle of the holding unit are fine-tuned by driving the lateral unit  4  and the theta unit  5  to fine-tune the whole elevating drive unit  6 . Subsequently, the elevating drive unit  6  lowers the gripper device  10  to place the FOUP  200  on the load port  300 , and the gripper device  10  releases its holding of the flange section  202  of the FOUP  200 . The elevating drive unit  6  then lifts the gripper device  10  to the lifting end thereof. The overhead conveyance vehicle  1  that does not hold the FOUP  200 , then begins traveling. 
     As illustrated in  FIG.  2   , the gripper device  10  includes an elevating section  11  that defines a body of the gripper device  10 , a motor  16  fixed to the elevating section  11 , a single link mechanism  20  connected to the motor  16  via an output shaft  16   a  of the motor  16 , and a pair of finger sections (engaging portions)  12  attached to respective tips of the link mechanism  20 . The motor  16 , the link mechanism  20 , and the pair of finger sections  12  are attached to the elevating section  11 . The motor  16  and the link mechanism  20  are included in the drive section  7  that moves the pair of finger sections  12 . The elevating section  11  is suspended by, for example, four belts  6   a  that are included in the elevating drive unit  6  described above. The elevating section  11  is capable of lifting and lowering above the FOUP  200  (above the load port  300 ) when the elevating drive unit  6  is controlled by the controller  8 . It should be noted that the elevating drive unit  6  may include three belts  6   a  and the elevating section  11  may be suspended by the three belts  6   a.    
     Referring to  FIG.  3   , the FOUP  200  held by the gripper device  10  of the present preferred embodiment is described. The FOUP  200  includes a body  201  having a rectangular parallelepiped shape, for example. A lid  205  is attached to a side surface of the body  201  (a surface of a side in the travel direction of the overhead conveyance vehicle  1 ) so as to be opened and closed freely. The FOUP  200  accommodates a plurality of semiconductor wafers in the body  201 . The FOUP  200  may accommodate a plurality of semiconductor panels that each are a rectangular-shaped substrate, within the body  201 . A top surface  201   a,  having a rectangular shape, of the body  201  is provided with a pair of flange sections  202  that are held by the gripper device  10 . The pair of flange sections  202  are spaced apart in a direction along the top surface  201   a  and corresponding to the travel direction of the overhead conveyance vehicle  1  (X direction indicated in the figure). In the following description, this direction is referred to as a “first direction”. The pair of flange sections  202  are disposed at ends  201   b  and  201   b  in an X direction of the top surface  201   a  and each extend long in a direction along the top surface  201   a  and orthogonal to the above-described first direction (Y direction indicated in the figure). In the following description, a direction orthogonal to this first direction is referred to as a “second direction”. These terms of the first direction and the second direction are able to be used to describe the FOUP  200 , and are able to also be used to describe the gripper device  10  that holds the FOUP  200 . As described above, the first direction corresponds to the travel direction of the overhead conveyance vehicle  1  in a state where the elevating drive unit  6  and the gripper device  10  are aligned with the frame unit  2 . 
     More specifically, a plurality of pairs (three pairs in the present preferred embodiment) of columns  203  are erected on the top surface  201   a  of the FOUP  200  at each of the ends  201   b  and  201   b.  The three columns  203  are spaced apart in the Y direction, and aligned in the Y direction, for example. Each of the columns  203  extends perpendicular to the top surface  201   a,  and its lower end is fixed to the top surface  201   a.  At one end  201   b  in the first direction of the top surface  201   a,  three equal-length columns  203 , for example, are erected, and one plate of the flange section  202  is fixed to the upper end of each of these columns  203  by welding or bolts. Each of the flange sections  202  is, for example, a long plate-shaped member that is disposed parallel to the top surface  201   a  and extends in the Y direction. At the other end  201   b  in the first direction of the top surface  201   a,  for example, three columns  203  having an equal length are erected, and one plate of the flange section  202  is fixed to the upper end of each of these columns  203  by welding or bolts. The pair of flange sections  202  extend parallel, for example, to the top surface  201   a  of the FOUP  200 . As explained above, the FOUP  200  has the pair of flange sections  202  provided on the top surface  201   a  and spaced apart in the first direction along the top surface  201   a.    
     When the column  203  is provided, a predetermined space is provided between the top surface  201   a  and the flange section  202 . As illustrated in  FIG.  1   , the pair of flange sections  202  fall within a length of the body  201  in the first direction (the overall length of the FOUP  200 ). The finger section  12  of the gripper device  10  is inserted into a space between the top surface  201   a  and the flange section  202 , from the center of the top surface  201   a  to the end  201   b.  The FOUP  200  is an article that is held (supported) from below by the finger section  12  that is moved from inside to outside and inserted into the above-described space. 
     Referring to  FIGS.  2 ,  4 , and  5   , the gripper device  10  is described in detail. The pair of finger sections  12  of the gripper device  10  move along the first direction (X direction indicated in the figure). The pair of finger sections  12  are supported by the elevating section  11  so as to be able to move (slide) horizontally in the gripper device  10 . When the gripper device  10  holds the FOUP  200 , the finger sections  12  advance to be closer to the flange section  202 . When the gripper device  10  releases its holding of the FOUP  200 , the finger sections  12  retreat so as to be away from the flange section  202 . 
     As illustrated in  FIGS.  2  and  4   , the link mechanism  20  moves the finger section  12 . The link mechanism  20  includes a single central link  17  that is connected to the output shaft  16   a  of the motor  16  and rotates about the output shaft  16   a,  a pair of first links  18  the first ends of which are rotatably connected to a pair of shafts  17   a  provided at both ends of the central link  17 , and a pair of second links  19  the base ends of which are rotatably connected to a pair of shafts  18   a  provided at the second ends of the first links  18 . As illustrated in  FIGS.  4  and  5   , as the output shaft  16   a  rotates, the central link  17  rotates, and one of the first links  18  and one of the second links  19  and the other of the first links  18  and the other of the second links  19  move synchronously. The finger section  12  is attached to the tip of each of the pair of second links  19 . 
     As illustrated in  FIG.  2   , the finger section  12  includes an engaging plate  13  that is rectangular in plan view. This engaging plate  13  is inserted into the space between the top surface  201   a  of the FOUP  200  and the flange section  202 , and supports the flange section  202  from below. The pair of finger sections  12  of the gripper device  10  engage with the pair of flange sections  202  of the FOUP  200 . 
     More specifically, as illustrated in  FIGS.  6  and  7   , the engaging plate  13  includes a thick plate section  13   a  attached to the tip of the second link  19  and a thin plate section  13   b  on the tip side of the thick plate section  13   a.  As illustrated in  FIG.  7   , the thin plate section  13   b  is thinner than the thick plate section  13   a.  A bottom surface of the thin plate section  13   b  is flush with a bottom surface of the thick plate section  13   a,  but a top surface of the thin plate section  13   b  is at a position lower than a top surface of the thick plate section  13   a,  and a single sheet of first buffer member  14  and two sheets of second buffer members  15  having predetermined thicknesses are affixed to the top surface of this thin plate section  13   b.  These first buffer member  14  and second buffer members  15  are, for example, resin members. The second buffer members  15  having a rectangular shape are affixed to both ends of the thin plate section  13   b  in the second direction, and the first buffer member  14  having a rectangular shape is affixed between the second buffer members  15 . 
     The position where the second buffer member  15  is affixed corresponds to the position of the center column  203  of the three columns  203  erected on the FOUP  200 . The thin plate section  13   b  and the first buffer member  14  have triangular notches having substantially equal size and shape formed therein. Accordingly, a notch  12   a  that accepts the center column  203  is formed in the finger section  12 . The notch  12   a  is, for example, a V-shaped depression containing two oblique edges and is open at a tip  12   b  of the finger section  12  in the X direction thereof. The length of the engaging plate  13  in the Y direction is shorter than the interval between the columns  203  located at both ends. In a state where the notch  12   a  in the finger section  12  accepts the central column  203  (i.e., the central column  203  fits in the notch  12   a ), the finger section  12  is disposed between the columns  203  located at both ends (see  FIG.  6   ). 
     Referring again to  FIGS.  4  and  5   , the range of movement of the finger section  12  is explained. The drive section  7  moves the pair of finger sections  12  along the first direction between a standby position P 1  (see  FIG.  4   ), where the distance between the pair of finger sections  12  is shorter than the interval between the pair of flange sections  202 , and an engaging position P 2 , where the pair of finger sections  12  is capable of engaging with the flange sections  202 . This engaging position P 2  is a position such that the distance between the pair of finger sections  12  is longer than the interval between the pair of flange sections  202 . In the present preferred embodiment, with the link mechanism  20 , the pair of finger sections  12  move linearly. The “distance between a pair of finger sections  12 ” is a distance between the tips  12   b  of the finger sections  12  indicated in  FIG.  4   . The “interval between the pair of flange sections  202 ” is the distance between inner ends  202   b  in the first direction of the pair of flange sections  202  indicated in  FIG.  4   . 
     In other words, the drive section  7  moves the pair of finger sections  12  along the first direction from the standby position P 1  to the engaging position P 2  such that the pair of finger sections  12  are separated from one another. In other words, the drive section  7  moves the pair of finger sections  12  from inside (closer to the center of the elevating section  11 ) to outside (closer to the front frame  22  and rear frame  23 ) of the elevating section  11 . Thus, the drive section  7  extends and deploys the pair of finger sections  12 . The drive section  7  moves the pair of finger sections  12  along the first direction from the engaging position P 2  to the standby position P 1  such that the pair of finger sections  12  are closer to each other. In other words, the drive section  7  moves the pair of finger sections  12  from outside (closer to the front frame  22  and rear frame  23 ) to inside (closer to the center of the elevating section  11 ) of the elevating section  11 . Thus, the drive section  7  retracts and stores the pair of finger sections  12 . 
     Furthermore, the gripper device  10  in the present preferred embodiment includes a drop preventing section  30  that prevents the FOUP  200  from dropping in a case where the device (the FOUP  200  or the finger section  12 ) is damaged. As illustrated in  FIGS.  2  and  5   , a pair of the drop preventing sections  30  are fixed to both ends of the elevating section  11  in the first direction. The pair of drop preventing sections  30  are disposed so as to be spaced apart in the first direction with an interval longer than the interval between the pair of flange sections  202 . More specifically, the pair of drop preventing sections  30  are spaced apart in the first direction by an interval longer than the distance between outer ends  202   a  (see  FIG.  8   ) of the pair of flange sections  202  in the first direction. Each of the drop preventing sections  30  includes a hanging plate  31  that hangs from the elevating section  11 . A lower end  31   a  of the hanging plate  31  is located at a lower height than the flange section  202  in a state where the gripper device  10  is lowered and the height of the gripper device  10  with respect to the FOUP  200  is adapted. More specifically, in a state where the finger section  12  engages with the flange section  202  and the gripper device  10  holds the FOUP  200  (the state indicated in  FIGS.  5  and  8   ), the lower end  31   a  of the hanging plate  31  is at a lower height than the flange section  202 , and an inner surface  31   b  of the hanging plate  31  faces the outer end  202   a  of the flange section  202  with a predetermined gap. 
     As illustrated in  FIG.  4   , a first gap G 1  is provided between each of the pair of drop preventing sections  30  and each of the pair of finger sections  12  located at the standby position P 1 , the first gap G 1  allowing each of the pair of flange sections  202  to vertically pass therethrough. As illustrated in  FIG.  8   , a second gap G 2  is provided between each of the pair of drop preventing sections  30  and each of the pair of finger sections  12  located at the engaging position P 2 , the second gap G 2  not allowing each of the pair of flange sections  202  to pass vertically therethrough. The first gap G 1  and the second gap G 2  may be defined as a distance between the tip  12   b  of the finger section  12  and the inner surface  31   b  of the hanging plate  31 . The first gap G 1  is larger than the flange section  202  in size in the first direction. The second gap G 2  is smaller than the flange section  202  in size in the first direction. 
     The following describes the conveyance method of the FOUP  200  by the overhead conveyance vehicle  1  including the gripper device  10  of the present preferred embodiment. Each of the following operations is performed based on control by the controller  8 . First, in a state where the horizontal position of the gripper device  10  is located directly above the load port  300 , the elevating section  11  is lowered (lowering step). In this lowering step, positioning of the gripper device  10  in the height direction and the horizontal direction relative to the FOUP  200  is performed using known positioning means or the like provided in the elevating section  11 . Then, the drive section  7  moves the pair of finger sections  12  along the first direction from the standby position P 1 , where the distance between the pair of finger sections  12  is shorter than the interval between the pair of flange sections  202 , to the engaging position P 2 , where the pair of finger sections  12  is capable of engaging with the flange sections  202  (for the moving step, see  FIGS.  4  and  5   ). This step allows the center column  203  to enter the notch  12   a  in the finger section  12 , and the finger section  12  to be inserted into the bottom surface side of the flange section  202 . Furthermore, the elevating section  11  is lifted and the pair of finger sections  12  at the engaging position P 2  engage with the pair of flange sections  202 , and the FOUP  200  is held by the gripper device  10  (holding step). 
     According to the gripper device  10  of the present preferred embodiment, the pair of finger sections  12  attached to the elevating section  11  is moved by the motor  16  from the standby position P 1  to the engaging position P 2 . The top surface  201   a  of the FOUP  200  is provided with a pair of flange sections  202  spaced apart in the first direction. The pair of finger sections  12  are disposed between (inside) these pairs of flange sections  202  when the gripper device  10  is to hold the FOUP  200 , and are moved from inside to outside of the FOUP  200  along the first direction above. This arrangement of the finger sections  12  and their movement and engagement in the first direction makes the gripper device  10  compact as a whole. According to this gripper device  10 , an article is able to be held in the compact configuration. 
     Since only one link mechanism  20  is used to move a pair of finger sections  12 , the structure is simpler than when multiple link mechanisms are used. In addition, since a single common link mechanism  20  is provided for the pair of finger sections  12 , the movements of the pair of finger sections  12  are able to be easily synchronized. 
     When the elevating section  11  is lowered in a state where the pair of finger sections  12  are located at the standby position P 1 , the flange section  202  passes through the first gap G 1  between the finger section  12  and the drop preventing section  30  in each of both end regions in the first direction (see  FIG.  4   ). When the pair of finger sections  12  are moved to the engaging position P 2  to engage with the pair of flange sections  202 , the flange sections  202  are not able to pass through the second gap G 2  between the finger section  12  and the drop preventing section  30  in each of both end regions in the first direction (see  FIG.  5   ). For example, as illustrated in  FIG.  9   , even if the first flange section  202  (or the first finger section  12 ) is damaged due to some unforeseen event, the second flange section  202  is held and maintained between the second finger section  12  and the second drop preventing section  30 . Thus, either one of the engagement structures can be maintained, and the FOUP  200  can be held and the FOUP  200  is able to be prevented from dropping. 
     When a proper engagement structure for the flange section  202  is not provided in any of the finger sections  12  (in a case as exemplified in  FIG.  9   ), the controller  8  may detect absence of the flange section  202 , upon receiving a signal from a known sensor (e.g., a presence sensor or the like) installed in a positioning section of the elevating section  11 , for example. The controller  8 , upon detecting absence of the flange section  202 , may generate an alarm or inform the operator of the absence. With this approach, it is possible to detect not only the absence of the flange section  202 , but also damage to the finger section  12 . 
     When the column  203  is provided on the FOUP  200 , a space into which the finger section  12  is inserted is able to be easily provided between the top surface  201   a  of the FOUP  200  and the flange section  202 . The column  203  defines and functions as a spacer. In the movement of the finger section  12  in the first direction, it is possible to perform control, for example, to make a portion of the finger section  12  contact the column  203  from the inside. In such a case, the finger section  12  is able to be positioned securely and easily. 
     According to the overhead conveyance vehicle  1  of the present preferred embodiment, since the gripper device  10  has the compact configuration, the overhead conveyance vehicle  1  is able to be made compact and lightweight relative to the FOUP  200  in the size, the weight, and the like. 
     According to the above-described conveyance method of the present preferred embodiment, the same actions and effects as those of the overhead conveyance vehicle  1  and gripper device  10  described above are achieved. In other words, in the holding step, the FOUP  200  is able to be held in the compact configuration. The gripper device  10  has the compact configuration, and is able to make use of the advantage that the device is compact and light weight when carrying the held FOUP  200 . For example, the conveyance method of the present preferred embodiment is also advantageous in terms of providing faster carrying speeds and reducing power consumption. 
     Although the preferred embodiments of the present disclosure have been described above, the present invention is not limited to the above-described preferred embodiments. For example, either one or both of the lower drop preventing section  26  and the lid drop preventing section  27  may be omitted. Not limited to cases where the plurality of pairs of columns  203  are erected on the top surface  201   a  of the FOUP  200 , only one pair of the pairs of columns  203  may be erected on the top surface  201   a  of the FOUP  200 . In other words, the columns  203  at both ends in the Y direction may be omitted. In such a case, the column  203  may be erected in substantially the center of the flange section  202  in an extending direction. The pair of flange sections  202  may be somewhat beyond the length of the body  201  in the first direction (the overall length of the FOUP  200 ). 
     Preferred embodiments of the present invention are not limited to cases where the drive section  7  has only one link mechanism  20 . The first finger section  12  and second finger section  12  may be driven separately. Each of the finger sections may be driven by a ball screw, a belt, or the like, for example, instead of the link mechanism. 
     The pair of engaging portions may be moved along the top surface  201   a  of the FOUP  200  in a direction that is linear and at an angle to the first direction. It is not limited to the case where the pair of engaging portions are moved linearly by the drive section, but the pair of engaging portions may be moved along the top surface  201   a  of the FOUP  200  in a zigzag manner, for example. The pair of engaging portions may be moved along the top surface  201   a  of the FOUP  200  in a curved shape, for example. 
     An article is not limited to the FOUP  200 . The article may be a standard mechanical interface (SMIF) pod or a front opening shipping box (FOSB), or the like. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.