Patent Publication Number: US-2023140218-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 to carry the article. 
     2. Description of the Related Art 
     A gripper device supporting storage containers is known, as described in Japanese Unexamined Patent Publication No. 2016-163001. This gripper device includes a center cone protruding downward at approximately a center of an elevating platform and a pair of finger sections that support storage containers from below. When the gripper device is lowered from above the storage container, the pair of finger sections are guided into a flange section of the storage container and the center cone is inserted into an insertion hole of the flange section. As a result, the gripper device is positioned with respect to the storage container. 
     SUMMARY OF THE INVENTION 
     In the conventional gripper device described above, only one center cone is used for positioning, which may result in insufficient positioning in a height direction. If positioning is performed by a center cone having a hemispherical outer surface, there is a risk of residual misalignment in a rotational direction around the center cone. 
     Preferred embodiments of the present disclosure provide gripper devices, conveyance vehicles, and conveyance methods capable of providing accurate positioning in a horizontal direction and a height direction for an article. 
     One aspect of a preferred embodiment of the present disclosure is a gripper device that holds an article placed on a transfer section, the gripper device including a holding portion that is attached to an elevating section capable of lifting and lowering above the transfer section to hold the article, a first positioning section that is attached to the elevating section to position the holding portion in a horizontal direction with respect to the article by contacting the article at two first contact positions in an upper portion of the article, and a second positioning section that is attached to the elevating section to position the holding portion in a height direction with respect to the article by contacting the article at three second contact positions that are not located on a straight line in the upper portion of the article. 
     According to this gripper device, the first positioning section contacts the article at the two first contact positions in the upper portion of the article. Contact of the first positioning section provides positioning of the holding portion in the horizontal direction with respect to the article. The second positioning section contacts the article at the three second contact positions in the upper portion of the article. Since these three second contact positions are not located on the straight line, the contact of the second positioning section provides positioning of the holding portion in the height direction with respect to the article. Thus, the two contact positions in the horizontal direction and the three contact positions in the height direction are used to allow accurate positioning of the article in the horizontal direction and the vertical direction. 
     The first positioning section may contact the article at only the two first contact positions. When the first positioning section contacts the article at the three or more first contact positions, the position of the holding portion in the horizontal direction is not likely to be uniquely determined between two of the three positions and the other one thereof, resulting in inconsistencies. In other words, competition may occur among the three or more first contact positions. When locations of the first contact positions are limited to only two locations, such inconsistencies, that is, the competition, can be prevented. 
     A position detected portion provided on a top surface of the article includes an opening opened upward and includes two guide holes of a tapered shape each having an inner diameter that decreases as a height of the tapered guide hole to the opening decreases, positions at which the two guide holes are respectively located are the two first contact positions and the two second contact positions, and the first positioning sections may include two convex members that are capable of entering the respective two guide holes. In this case, the two first contact positions and the two second contact positions are made common, which makes it possible to reduce positioning sections in the number. 
     The second positioning section may include at least one pressing portion including a horizontal surface portion that contacts the position detected portion provided on the top surface of the article at at least one of the second contact positions. According to the pressing portion including a horizontal surface portion, positioning in the height direction can be performed accurately and easily. 
     There may be provided the four second contact positions at respective four locations. In this case, positioning can be performed more accurately in the height direction. 
     As another aspect of a 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, the holding portion holds the article in a state of being accurately positioned with respect to the article. Thus, the carrying state of the article becomes stable, which makes it possible to carry the article at a high speed. 
     Another aspect of a preferred embodiment of the present disclosure is a conveyance method for holding to carry an article placed on a transfer section by a gripper device, in which the gripper device includes a holding portion that is attached to an elevating section capable of lifting and lowering above the transfer section to hold the article, a first positioning section to perform positioning in a horizontal direction with respect to the article, and a second positioning section to perform positioning in a height direction with respect to the article, the method including a lowering step of lowering the elevating section, a first positioning step of positioning the holding portion in the horizontal direction with respect to the article by bringing the first positioning section into contact with the article at two first contact positions in an upper portion of the article, the first positioning step being performed after the lowering step, a second positioning step of positioning the holding portion in the height direction with respect to the article by bringing the second positioning sections into contact with the article at three second contact positions that are not located on a straight line in the upper portion of the article, the second positioning step being performed after the lowering step and a holding step of holding the article by the holding portion, the holding step being performed after the first positioning step and the second positioning step. 
     According to this conveyance method, the same actions and effects as described above are achieved. In other words, the two contact positions are used in the horizontal direction and the three contact positions are used in the height direction to allow accurate positioning of the article in the horizontal direction and the height direction. 
     According to preferred embodiments of the present disclosure, positioning in the horizontal direction and the height direction to an article can be accurately performed. 
     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 schematic diagram illustrating 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 cross-sectional view of a structure of a first positioning section. 
         FIG.  5    is a cross-sectional view of the structure of the second positioning section. 
         FIG.  6    is a diagram illustrating arrangement of the first positioning section and the held portion of the article in a first positioning process. 
         FIG.  7    is a diagram illustrating a state in which the elevating section is lowered following the state indicated in  FIG.  6   . 
         FIG.  8    is a diagram indicating a state in which the elevating section is lowered following the state indicated in  FIG.  7   . 
         FIG.  9    is a diagram indicating the state in which the holding portion has moved to the engaging position of the held portion following the state indicated in  FIG.  8   . 
         FIG.  10    is a diagram indicating the state in which the holding portion engages with the held portion to hold the article following the state illustrated in  FIG.  8   . 
         FIGS.  11 A to  11 D  are diagrams indicating various variations on the arrangement of the first contact position and the second contact position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As illustrated in  FIG.  1   , an overhead conveyance vehicle (conveyance vehicle)  1  according to a preferred embodiment 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 present preferred 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  (transfer section) 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 surface. 
     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  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  is configured or programmed to control 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  and a holding portion  9  that holds the FOUP  200 . The holding portion  9  includes 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 a drive section  7  that moves the pair of finger sections  12 . Each of the pair of finger sections  12  may be driven by a ball screw, a belt, or the like, for example, instead of the link mechanism  20 . 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 have 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 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 (for example, 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 . 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. 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 exists 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 held (supported) from below by the finger section  12  that is moved from inside to outside and inserted into the above-described space. 
     The pair of finger sections  12  of the gripper device  10  moves along the first direction (X direction indicated in the figure). 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 on the FOUP  200 , the finger sections  12  retreat so as to be away from the flange section  202 . 
     As illustrated in  FIG.  2   , the link mechanism  20  is a mechanism for moving 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 the output shaft  16   a  rotates, the central link  17  rotates, and the first link  18  and the second link  19  on one side and the first link  18  and the second link  19  on the other side move synchronously. The finger section  12  is attached to the tip of each of the pair of second links  19 . The finger section  12  includes a notch  12   a  that accepts the central column  203 . 
     The gripper device  10  of the present preferred embodiment is provided with a positioning mechanism to position the holding portion  9  with respect to the FOUP  200 . The need for proper positioning for articles is as described in the above-described Japanese Unexamined Patent Publication No. 2016-163001. Proper positioning ensures that the finger section  12  (holding portion  9 ) of the gripper device  10  has a correct position and orientation and a suitable engagement and retention with the FOUP  200 . The positioning mechanism provided in the gripper device  10  enables more accurate positioning in cooperation with the position detected portion and the contact position that the FOUP  200  has. 
     As illustrated in  FIG.  2   , the gripper device  10  has the four positioning sections attached to the elevating section  11 . More specifically, the gripper device  10  is provided with positioning sections at the four corner positions of the elevating section  11  having a rectangular shape in plan view. Two first positioning sections  40  are attached on one diagonal of the elevating section  11  (upper left and lower right corners indicated in  FIG.  2   ). These first positioning sections  40  basically position the holding portion  9  in the horizontal direction (along the XY plane) to the FOUP  200 . Two second positioning sections  50  are attached on the other diagonal of the elevating section  11  (upper right and lower left corners indicated in  FIG.  2   ). These second positioning sections  50  position the holding portion  9  in the height direction (Z direction indicated in  FIG.  1   ) to the FOUP  200 . 
     Before describing the structure of the first positioning section  40  and the second positioning section  50 , the structure of the FOUP  200  according to the positioning mechanism is described with reference to  FIG.  3   . As illustrated in  FIG.  3   , the flange sections  202  of the FOUP  200  are long, flat plate members each extending long in the second direction and parallel to the top surface  201   a  of the FOUP  200 . A flange top surface  202   a  of each flange section  202  is flat and parallel to the top surface  201   a . The flange top surface  202   a  is a position detected surface (position detected portion) provided on the top surface  201   a  of the FOUP  200 , and enables, when contacting the first positioning section  40  and the second positioning section  50 , positioning of the holding portion  9  in the height direction. 
     Two guide holes  206  are located at both ends of each flange section  202  in the second direction. These guide holes  206  have the same size and shape. Each of the guide holes  206  has an inverted conical trapezoidal shape and penetrates the flange section  202  in a thickness direction. Each of the guide holes  206  has a circular opening that is open upward and has a conical tapered shape with a smaller inner diameter downward. In other words, in each of the guide holes  206 , the lower the height of the top end to the opening, the smaller the inside diameter. In the pair of flange sections  202 , the guide holes  206  are symmetrical with respect to a hypothetical central plane orthogonal to the first direction (plane containing an axis of the output shaft  16   a ). The positions of these four guide holes  206  correspond to the positions of the first positioning sections  40  and the second positioning sections  50  in plan view. More precisely, when the holding portion  9  is in an exact position with respect to the FOUP  200 , the positions of the central axes of the four guide holes  206  coincide with the positions of the shafts  42  of the first positioning section  40  and the shafts  52  of the second positioning section  50 , as described below. Of the four guide holes  206 , the two guide holes  206  disposed on the first diagonal enable, when contacting the first positioning section  40 , positioning in the horizontal direction of the holding portion  9  . At the same time, the two guide holes  206  disposed on the first diagonal also enable, when contacting the two first positioning sections  40 , positioning of the holding portion  9  in the height direction. 
     The two second positioning sections  50 , out of the four guide holes  206 , do not contact the two guide holes  206  disposed on the second diagonal. In the present preferred embodiment, the two second positioning sections  50  only contact the flange top surface  202   a  at the position where the two guide holes  206  disposed on the second diagonal are located. The versatility of FOUP  200  is enhanced by the fact that the FOUP  200  has four guide holes  206 . The four guide holes  206  can be used, for example, when the FOUP  200  is handled by an automated guided vehicle (AGV), which is another transport system different from the overhead conveyance vehicle  1  in the present preferred embodiment. 
     Referring to  FIGS.  2 ,  4 , and  5   , the structures of the first positioning section  40  and the second positioning section  50 , respectively, are described. As illustrated in  FIGS.  2  and  4   , the first positioning section  40  includes a sensor box  45  fixed to a corner of the elevating section  11 , a shaft  42  capable of moving in a vertical direction with respect to the sensor box  45 , and a convex member  41  fixed to the lower end of the shaft  42 . The sensor box  45 , for example, is open in a vertical direction and its side surface is fixed to an outer side surface of the elevating section  11 . The convex member  41  may include a conical surface portion  41   a . The conical surface portion  41   a  has a shape corresponding to the guide hole  206 , for example, to engage with the guide hole  206  in the flange section  202 . In other words, a portion of the conical surface portion  41   a  of the convex member  41  has a shape that substantially coincides with a peripheral wall surface of the guide hole  206 . A spring  43  is interposed between the bottom of the sensor box  45  and the convex member  41  around the shaft  42 . The spring  43  exerts a force with respect to the convex member  41  and the sensor box  45  in a direction of being spaced apart from each other. 
     A position detection plate  44  is fixed to an upper end of the shaft  42 . A seating sensor  46  and a presence sensor  47  are installed in opposing positions in an upper portion of the inside of the sensor box  45 . The seating sensor  46  and the presence sensor  47  are fixed to the sensor box  45  and detect presence of a first detected piece  44   a  and a second detected piece  44   b  according to a relative movement of the position detection plate  44  in the sensor box  45 . The seating sensor  46  is a sensor that detects seating of the holding portion  9  (i.e., whether the convex member  41  is inserted into the guide hole  206  of the flange section  202 ). The presence sensor  47  is a sensor that detects the presence of the FOUP  200  in a state in which the FOUP  200  is lifted. For example, if the FOUP  200  is absent, the presence sensor  47  is turned off and an abnormal alarm is issued. As an absence of the FOUP  200 , for example, loss of engagement of the FOUP  200  to the finger section  12  due to falling of the flange section  202  can be considered. Cables to output signals to the controller  8  are connected to the seating sensor  46  and the presence sensor  47 . The detection operations of these sensors associated with the lifting and lowering of the elevating section  11  and the holding of the FOUP  200  by the gripper device  10  are described below. 
     As illustrated in  FIGS.  2  and  5   , the second positioning section  50  includes a box  55  fixed to a corner of the elevating section  11 , a shaft  52  capable of moving in a vertical direction with respect to the box  55 , and a flat plate-shaped pressing member  51  fixed to the lower end of the shaft  52 . The box  55 , for example, is open in a vertical direction, and its side surface is fixed to the outer side surface of elevating section  11 . The pressing member  51  may include a horizontal surface portion  51   a  that contacts the flange top surface  202   a  of the FOUP  200 . The lower end of the shaft  52  may somewhat protrude from a bottom surface of the pressing member  51 . In a state in which the horizontal surface portion  51   a  is in contact with the flange top surface  202   a , a protruding portion of the shaft  52  is disposed inside the guide hole  206 . A spring  53  is interposed between the bottom of the box  55  and the pressing member  51  around a shaft  52 . The spring  53  exerts a force with respect to the pressing member  51  and the box  55  in the direction of being spaced apart from each other. 
     In the first positioning section  40  and the second positioning section  50 , the height of the convex member  41  to the guide hole  206  and the height of the pressing member  51  to the flange top surface  202   a  are equal. In other words, in a state in which the conical surface portion  41   a  of the convex member  41  contacts the peripheral wall surface of the guide hole  206  and the horizontal surface portion  51   a  of the pressing member  51  contacts the flange top surface  202   a , and the force (repulsive force) received from the spring  43  and the force from spring  53  are equal, the elevating section  11  and the holding portion  9  are parallel with respect to the top surface  201   a  of the FOUP  200  in the posture. In other words, the holding portion  9  is positioned in the height direction with respect to the FOUP  200 . In other words, in a state in which the convex member  41  contacts the peripheral wall surface of the guide hole  206  (convex member  41  fits into the guide hole  206 ), the pressing member  51  contacts (rides on) the flange top surface  202   a , and the elevating section  11  and the holding portion  9  that are suspended by the four belts  6   a  are on the flange section  202  with their own weights, the holding portion  9  is positioned in the height direction with respect to the FOUP  200 . Moreover, in this state, the holding portion  9  is also positioned horizontally with respect to the FOUP  200  by fitting (fitting of a tapered shape) of the convex member  41  with respect to the guide hole  206 . 
     In the gripper device  10  and the FOUP  200  having the above-described configuration, as illustrated in  FIG.  3   , positions at which the two guide holes  206  disposed on the first diagonal in the flange section  202  are located are two first contact positions Pa that the first positioning section  40  contacts. The holding portion  9  is positioned in the horizontal direction with respect to the FOUP  200  when the first positioning section  40  contacts the FOUP  200  at the two first contact positions Pa in the upper portion of the FOUP  200 . 
     In the flange section  202 , the two guide holes  206  disposed on the first diagonal are also the two second contact positions Pb that the first positioning section  40  contacts. In addition, positions at which the two guide holes  206  disposed on the second diagonal are located are the two second contact positions Pb that the second positioning section  50  contacts. The holding portion  9  is positioned in the height direction with respect to the FOUP  200 , when the first positioning section  40  and the second positioning section  50  contact the FOUP  200  at the four second contact positions Pb in the upper portion of the FOUP  200 . 
     The first contact position Pa is a contact position for positioning of the holding portion  9  in the horizontal direction in the upper portion of the FOUP  200 . The second contact position Pb is a contact position for positioning of the holding portion  9  in the height direction in the upper portion of the FOUP  200 . In the present preferred embodiment, positions at which the two guide holes  206  disposed on the first diagonal are located are the two first contact positions Pa and the two second contact positions Pb. The first positioning section  40  includes two convex members  41  that are capable of entering the respective two guide holes  206 . This configuration allows the first positioning section  40  to also position the holding portion  9  in the height direction and to perform (serve) the same function as the second positioning section  50 . 
     In other words, in the present preferred embodiment, the first positioning section  40  contacts the FOUP  200  at only the two first contact positions Pa for positioning in the horizontal direction. The four second contact positions Pb for positioning in the height direction are provided at four respective locations. In other words, the gripper device  10  positions the holding portion  9  in the horizontal direction and the vertical direction by bringing the convex member  41  of the first positioning section  40  into contact with the two guide holes  206  as the first contact position Pa and the second contact position Pb. The gripper device  10  positions the holding portion  9  in the height direction by bringing the pressing member  51  of the second positioning section  50  into contact with the two guide holes  206  as the second contact position Pb. The first positioning section  40  performs (serves) the same function as the second positioning section  50  in some of the locations (two locations in the present preferred embodiment) out of the required three or more locations of positioning in the height direction. These second contact positions Pb are not located on the straight line. In other words, when three of the four second contact positions Pb are selected, they are not located on the straight line. The phrase “three second contact positions are not located on the straight line” means, for example, that if contact portions (contact surfaces) at the respective second contact positions have an area, a line connecting three center points of those contact portions is not in a straight line. The phrase “the three second contact positions are not located on the straight line” means that the plane containing the three center points is uniquely defined. 
     The following describes the conveyance method of the FOUP  200  by the gripper device  10  and the overhead conveyance vehicle  1  of the present preferred embodiment. First, when the elevating section  11  arrives above the load port  300 , the controller  8  lowers the elevating section  11  (lowering step). In this lowering step, the elevating section  11  is lowered until the seating sensor  46  turns ON. After the lowering step, the holding portion  9  is positioned in the horizontal direction with respect to the FOUP  200  by bringing the first positioning section  40  into contact with the FOUP  200  at the two first contact positions Pa in the upper portion of the FOUP  200  (first positioning step). After the lowering step, the holding portion  9  is positioned in the height direction with respect to the FOUP  200  by bringing the first positioning section  40  and the second positioning section  50  into contact with the FOUP  200  at the four second contact positions Pb that are not located on the straight line in the upper portion of the FOUP  200  (second positioning step). The first positioning step and the second positioning step are performed at substantially the same time. After these first and second positioning steps, the FOUP  200  is held by the holding portion  9  (holding step). 
     Referring to  FIGS.  6  to  10   , the following describes the first positioning step and the holding step. In accordance with the lowering of the elevating section  11 , as illustrated in  FIG.  6   , the convex member  41  enters (is inserted) into the guide hole  206 . At this point, the conical surface portion  41   a  of the convex member  41  contacts the peripheral wall surface of the guide hole  206  for the first time. Next, as illustrated in  FIG.  7   , the elevating section  11  and holding portion  9  are further lowered, and the seating sensor  46  turns ON. During this time, the presence sensor  47  switches from OFF to ON and then to OFF, but this switching of the presence sensor  47  is ignored because the seating sensor  46  remains OFF. Next, as illustrated in  FIG.  8   , when the elevating section  11  and the holding portion  9  are further lowered for a predetermined distance, their lowering stops. The series of steps described above completes the first positioning step. At the same time, the second positioning step is completed. 
     Next, as illustrated in  FIG.  9   , with the seating sensor  46  turned on, the drive section  7  moves the finger section  12 , and the finger section  12  is inserted into the space below the flange section  202 . Then, as illustrated in  FIG.  10   , the elevating section  11  and holding portion  9  are lifted and the flange section  202  (FOUP  200 ) is held by the finger section  12 . The foregoing step completes the holding step. Then, the elevating section  11  and holding portion  9  are lifted until they reach inside the frame unit  2 . 
     According to the gripper device  10  of the present preferred embodiment and the above-described conveyance method, the first positioning section  40  contacts the FOUP  200  at the two first contact positions Pa in the upper portion of the FOUP  200 . The contact of the first positioning section  40  provides positioning of the holding portion  9  in the horizontal direction with respect to the FOUP  200 . The first positioning section  40  and the second positioning section  50  contact the FOUP  200  at at least three second contact positions Pb (four in the present preferred embodiment) in the upper portion of the FOUP  200 . Since these second contact positions Pb are not located on the straight line, the contact of the first positioning section  40  and the second positioning section  50  provides positioning of the holding portion  9  in the height direction with respect to the FOUP  200 . Thus, two contact positions in the horizontal direction and at least three contact positions in the height direction are used, positioning with respect to the FOUP  200  in the horizontal and height directions can be accurately performed. 
     When the first positioning section  40  contacts the FOUP  200  at three or more first contact positions, the position of the holding portion  9  in the horizontal direction is not likely to be uniquely determined at two of the three positions and at one other position, resulting in inconsistencies. In other words, a competition may occur among the three or more first contact positions. If the number of locations of the first contact position Pa is limited to only two locations, such inconsistency, that is, a competition, is suppressed. 
     The first positioning section  40  functions similarly to the second positioning section by having two convex members  41  capable of entering the respective two guide holes  206 . The two first contact positions and the two second contact positions are made common, which makes it possible to reduce components for positioning in the number. 
     According to the pressing member  51  including the horizontal surface portion  51   a , positioning in the height direction can be performed accurately and easily. 
     Since the four second contact positions are provided at the respective four locations, positioning can be performed in the height direction more precisely. 
     According to the overhead conveyance vehicle  1 , the holding portion holds the FOUP  200  in a state of being precisely positioned with respect to the FOUP  200 . Therefore, the FOUP  200  can be transported in a stable condition, and thereby the FOUP  200  can be carried at high speed. 
     Although the preferred embodiments of the present disclosure has been described above, the present invention is not limited to the above-described preferred embodiments. For example, the arrangement of the first contact position Pa and the second contact position Pb may be modified to provide various aspects. As illustrated in  FIG.  11 A , the two first contact positions Pa (which also serve as the second contact positions due to the tapered shape) may be set on one flange section  202  and the two second contact positions Pb may be set on the other flange section  202 . It is not limited to a case where the contact positions of the same type are disposed on the diagonal as in the above-described preferred embodiment, but the contact positions of the same type may be disposed on the same side in the second direction, as illustrated in  FIG.  11 B . In this case also, the first contact position Pa also serves as the second contact position due to the tapered shape. As illustrated in  FIG.  11 C , the two first contact positions Pa (which also serve as the second contact positions due to the tapered shape) may be set on one flange section  202  and one second contact position Pb may be set on the other flange section  202 . As illustrated in  FIG.  11 D , the two first contact positions Pa (which also serve as the second contact positions due to the tapered shape) may be set on one flange section  202  and one large (extensive) second contact position Pb on the other flange section  202 . Having the extensive second contact position Pb provides the same stability as including a plurality of the second contact positions Pb. 
     The position detected portion that the first positioning section and the second positioning section contact may be provided at an appropriate position on the upper portion of the article. The flange section need not be installed on the top surface of the article, and the position detected portion may be provided on a portion other than the flange section. The position detected portion can be set as a horizontal surface (surface parallel to the top surface  201   a  of the body  201 ). It is not limited to a case where the holding portion engages with the flange section, and the holding portion may engage with any portion of the upper portion (including a side surface) of the article. The configuration of the holding portion is not limited to the above-described preferred embodiment. The aspect of the engaging portion of the holding portion is not limited to an aspect in which the engaging portion of the holding portion is moved from the inside to the outside. The engaging portion of the holding portion may be moved from the outside toward the inside. 
     The aspect of the first positioning section and the second positioning section is not limited to an aspect in which positioning includes a spring mechanism. The first positioning section and the second positioning section may include elastic members other than springs or need not include elastic members. The first positioning section and the second positioning section may include a damper mechanism. The second positioning section may be a flat plate member in which a position with respect to the elevating section  11  is fixed. 
     In the above-described preferred embodiment, sensors (seating sensor  46  and presence sensor  47 ) are installed in the first positioning section  40 . In contrast to this aspect, no sensor need be installed in the first positioning section  40 , and a sensor (for example, the seating sensor or the presence sensor that is similar to that disclosed in the above-described preferred embodiments) may be installed in the second positioning section  50 . These sensors may be installed in both the first positioning section  40  and the second positioning section  50 . In other words, these sensors may be installed at the four corners of the elevating section  11 . 
     In the above-described preferred embodiment, a guide hole  206  is provided that passes through the flange section  202 . The aspect is not limited to this aspect, and a guide hole of a tapered shape having a bottom (not passing through the flange section  202 ) may be provided. Furthermore, the aspect is not limited to an aspect in which the conical guide hole  206  is provided in the article. For example, the first positioning section may have a cylindrical convex member and a cylindrical hole (a through-hole) may be provided at any portion on the upper portion of the article. In this case, because positioning cannot be performed at the first positioning section in the height direction, at least three second contact positions need to be provided on the article, at locations other than those of the two first contact positions. 
     In other words, the aspect is not limited to the aspect in which the first contact position also serves as the second contact position. The two first contact positions and the three or more second contact positions may be provided separately. Alternatively, one of the two first contact positions may also serve as the second contact position. In both aspects, the gripper device includes the first positioning section corresponding to the first contact position and the second positioning section corresponding to the second contact position. When a certain first contact position also serves as a second contact position in the article, the first positioning section corresponding to that certain first contact position in the gripper device performs the same function as the second positioning section. 
     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.