Patent Publication Number: US-2023150123-A1

Title: Fulcrum opening/closing type air chuck

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-187797 filed on Nov. 18, 2021, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a fulcrum opening/closing type air chuck including a pair of pivoting gripping members, and more particularly to a fulcrum opening/closing type air chuck having a dust-proof function. 
     Description of the Related Art 
     Conventionally, there has been known a fulcrum opening/closing type air chuck that grips a workpiece using a pair of gripping members that pivot about axes. For example, JP H10-080888 A discloses a chuck device in which a pair of gripping members pivotably supported on a body are driven by a cylinder mechanism. 
     In the chuck device disclosed in JP H10-080888 A, a cover member is attached to one end portion of a body to prevent dust from entering the interior of the body. Specifically, a first curved portion provided on the pivoting portion of each gripping member is brought into contact with the corner portion of the body, and a second curved portion provided on the pivoting portion of the gripping member is brought into contact with the recess of the cover member. 
     SUMMARY OF THE INVENTION 
     However, in order to bring the pivoting portions of the gripping members into contact with the body and the cover member with substantially no gap, the dimensional accuracy of each member must be extremely high. Further, if it is attempted to bring them into contact with each other with no gap, the sliding resistance when the gripping members pivot becomes large. 
     As an anti-dust measure, a rubber dust cover covering the outer side of the gripping members may be attached to the body. However, unlike the gripping members of the parallel opening/closing type air chuck in which the gripping members are slid, the gripping members of the fulcrum opening/closing type air chuck have a large movable range. For this reason, in order to prevent the dust cover from coming into contact with the gripping members and being torn, a large dust cover is required, and the apparatus becomes large. 
     As another anti-dust measure, a rubber sealing member such as a gasket may be disposed between the gripping members and the body. However, when a rubber sealing member is used, the sliding resistance when the gripping members pivot becomes large. 
     The present invention has the object of solving the aforementioned problems. 
     The present invention is a fulcrum opening/closing type air chuck in which a pair of fingers are each supported so as to be pivotable about a pivot support shaft attached to a body, and a drive unit configured to drive the pair of fingers to move away from each other and approach each other is disposed inside the body. The fulcrum opening/closing type air chuck includes a porous body attached to the body and configured to come into contact with the fingers, and purge air passes through the porous body and is discharged to outside. 
     The fulcrum opening/closing type air chuck according to the present invention is provided with the porous body that is attached to the body and comes into contact with the fingers, and the purge air passes through the porous body and is discharged to the outside. Therefore, dust can be prevented from entering the interior of the body without increasing the sliding resistance of the fingers. 
     The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a fulcrum opening/closing type air chuck according to an embodiment of the present invention; 
         FIG.  2    is a plan view of the fulcrum opening/closing type air chuck shown in  FIG.  1   ; 
         FIG.  3    is a cross-sectional view taken along line III-III of  FIG.  2   ; 
         FIG.  4    is a cross-sectional view taken along line IV-IV of  FIG.  2   ; 
         FIG.  5    is a view showing a state in which a first porous body of the fulcrum opening/closing type air chuck shown in  FIG.  1    is attached; 
         FIG.  6    is a perspective view of a second porous body of the fulcrum opening/closing type air chuck shown in  FIG.  1   ; 
         FIG.  7    is a perspective view of a third porous body of the fulcrum opening/closing type air chuck shown in  FIG.  1   ; 
         FIG.  8    is a view showing a state in which the third porous bodies of the fulcrum opening/closing type air chuck shown in  FIG.  1    are attached; 
         FIG.  9    is a view showing the flow of purge air in the fulcrum opening/closing type air chuck shown in  FIG.  1   ; 
         FIG.  10    is a view corresponding to  FIG.  3    when a pair of fingers of the fulcrum opening/closing type air chuck shown in  FIG.  1    move away from each other; and 
         FIG.  11    is a view corresponding to  FIG.  3    when the pair of fingers of the fulcrum opening/closing type air chuck shown in  FIG.  1    approach each other. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     As shown in  FIGS.  1  to  4   , a fulcrum opening/closing type air chuck  10  according to an embodiment of the present invention includes a body  12 , a pair of fingers  80 , a drive unit  58 , and first to third porous bodies  94 ,  96 , and  110 . The pair of fingers  80  are pivotably supported on the body  12 . The drive unit  58  includes a piston  60  and a drive rod  70  integrally coupled to the piston  60 , and is disposed inside the body  12 . The pair of fingers  80  are driven to move away from each other and approach each other by the drive unit  58 . In the following description, when terms in relation to up and down directions are used, for the sake of convenience, such terms refer to the directions shown in  FIG.  3   , however, the actual arrangement of the constituent members and the like is not necessarily limited to this feature. 
     The body  12  includes a main body  14  and an end plate  48 . The end plate  48  is attached to the upper end of the main body  14  by screw members  52 . The main body  14  having a quadrangular prism shape includes a cylinder hole  16  therein, and the piston  60  is slidably disposed in the cylinder hole  16 . The lower end of the cylinder hole  16  is closed by a cap  54 . A cylinder chamber formed by the cylinder hole  16  is partitioned into a first pressure chamber  18  located above the piston  60 , and a second pressure chamber  20  located below the piston  60 . The main body  14  is provided with a first port  22  for supplying/discharging air to/from the first pressure chamber  18 , and a second port  24  for supplying/discharging air to/from the second pressure chamber  20 . 
     The main body  14  is cut out parallel to wide side surfaces  30  from one of a pair of narrow side surfaces  34  to the other thereof above the cylinder hole  16 . That is, the main body  14  includes a pair of side walls  28  above the cylinder hole  16 . Reference numeral  47  denotes attachment holes for attaching the body  12  to a conveying device (not shown) or the like. 
     A piston packing  62 , magnets  64 , and a wear ring  66  are mounted to the outer peripheral portion of the piston  60 . The piston packing  62  provides a seal between the first pressure chamber  18  and the second pressure chamber  20 . The wide side surfaces  30  of the main body  14  have sensor grooves  32 . The magnetic flux of the magnets  64  can be detected by magnetic sensors (not shown) attached to the sensor grooves  32 . A damper  68  is attached to the upper end of the piston  60 . The damper  68  absorbs an impact when the piston  60  moves to an upper end position. 
     The drive rod  70  is inserted into a bush  72  mounted to the cylinder hole  16 , and is supported so as to be movable up and down. A rod packing  74  in sliding contact with the drive rod  70  is mounted to the upper end of the cylinder hole  16 . The rod packing  74  airtightly holds the first pressure chamber  18 . A sealing member  56  for keeping the second pressure chamber  20  airtight from the outside is mounted to the outer peripheral portion of the cap  54 . The drive rod  70  extends upward from the cylinder hole  16 . The upper end of drive rod  70  is provided with a pair of arm portions  76  directed toward the respective fingers  80 . A cylindrical rolling element  78  is rotatably supported at the distal end of each arm portion  76 . 
     Each finger  80  is formed of a fan-shaped pivoting portion  82  and an elongated gripping portion  92 . The pivoting portion  82  and the gripping portion  92  have a constant width W 0 . The pivoting portion  82  is disposed between the pair of side walls  28  of the main body  14 . A pivot support shaft  40  is mounted across the pair of side walls  28  of the main body  14 , and the pivot support shaft  40  is inserted into a bush  88  mounted to the center of the pivoting portion  82 . As a result, the fingers  80  are supported so as to be pivotable about the pivot support shafts  40 . 
     The pivoting portions  82  each include a first curved surface  84  facing the end plate  48 , and a second curved surface  86  facing a fitting recess  42  of the main body  14  described later. The first curved surface  84  and the second curved surface  86  each have a constant radius of curvature about the axis of the pivot support shaft  40 . The radius of curvature of the first curved surface  84  is greater than the radius of curvature of the second curved surface  86 . Further, the pivoting portion  82  has two end surfaces facing the side walls  28  of the main body  14 . The end surfaces of the pivoting portion  82  are perpendicular to the axis of the pivot support shaft  40 . The gripping portions  92  each extend radially outward from one circumferential end portion of the first curved surface  84  of each of the pivoting portions  82 . 
     The pivoting portions  82  each include a groove portion  90  extending to a predetermined depth from another circumferential end portion of the first curved surface  84 . The rolling elements  78  supported by the arm portions  76  of the drive rod  70  are disposed in the groove portions  90  of the pivoting portions  82 , and can move in the groove portions  90  while rolling. As a result, the vertical linear motion of the drive rod  70  is converted into the pivot motion of the fingers  80 . When the drive rod  70  moves upward, the pair of fingers  80  pivot in a direction in which the pair of gripping portions  92  move away from each other, and when the drive rod  70  moves downward, the pair of fingers  80  pivot in a direction in which the pair of gripping portions  92  approach each other. 
     The end plate  48  includes, at both ends thereof, cutout portions  50  to be passages of the gripping portions  92  when the fingers  80  pivot. The narrow side surfaces  34  of the main body  14  each have an opening  36  that opens between the pair of side walls  28 . The pivoting portions  82  of the fingers  80  and the first to third porous bodies  94 ,  96 , and  110  prevent the interior of the body  12  from being directly connected to the outside through the openings  36  of the main body  14  and the cutout portions  50  of the end plate  48 . That is, a purge air storage space  38  isolated from the outside is formed above the cylinder hole  16 . 
     The first to third porous bodies  94 ,  96 ,  110  are each formed of a lubricant retainer that is a fiber composite. However, the first to third porous bodies  94 ,  96 , and  110  are not impregnated with a lubricant. The first to third porous bodies  94 ,  96 , and  110  cannot prevent fine dust from entering the interior by themselves due to the nature of having voids therein. However, by performing air purging described later, it is possible to prevent fine dust from entering from the outside. 
     The first to third porous bodies  94 ,  96 , and  110  that come into contact with the fingers  80  have small deformation resistance and are easily deformed. Even if the first to third porous bodies  94 ,  96 , and  110  are brought into contact with the fingers  80  at a predetermined pressure in order to reliably fill the gap between the first to third porous bodies  94 ,  96 , and  110  and the fingers  80 , resistance (sliding resistance) when the fingers  80  move is small. In the present embodiment, the first to third porous bodies  94 ,  96 , and  110  are formed of lubricant retainers, but may be formed of felt or sponge. 
     As shown in  FIG.  5   , the first porous body  94  is formed in an elongated rectangular plate shape having a constant width W 1 . The first porous body  94  is attached to the lower surface of the end plate  48  using, for example, an adhesive. The width W 1  of the first porous body  94  is equal to or slightly larger than the width W 0  of the pivoting portions  82  of the fingers  80 . In the entire pivot range of the fingers  80 , the first curved surface  84  of the pivoting portion  82  of each of the fingers  80  comes into contact with the end portion of the first porous body  94  in the lengthwise direction (see  FIG.  3   ). A portion of the first porous body  94  that comes into contact with the first curved surface  84  is deformed by being pressed by the first curved surface  84 . 
     As shown in  FIG.  6   , the second porous body  96  includes an elongated plate-shaped base portion  98 , and a pair of stepped portions  106  bent in an L-shape from both ends of the base portion  98 . The base portion  98  is provided with, at the center thereof in the lengthwise direction, a first hole portion  100  through which the drive rod  70  is inserted. Further, the base portion  98  is provided with, at one end portion thereof in the lengthwise direction, a second hole portion  102  serving as a passage of purge air. The base portion  98  is provided with a pair of projecting portions  104  projecting from the vicinity of the first hole portion  100  to both sides. In a state before the drive rod  70  is inserted into the first hole portion  100 , the inner diameter of the first hole portion  100  is smaller than the outer diameter of the drive rod  70 . In other words, when the drive rod  70  is inserted into the first hole portion  100 , the first hole portion  100  expands. 
     As shown in  FIG.  3   , the second porous body  96  is attached to the main body  14  so as to face the second curved surfaces  86  of the pivoting portions  82  of the fingers  80 . The main body  14  includes the fitting recess  42  whose bottom surface is a surface where the upper end of the cylinder hole  16  is opened. The second porous body  96  including the stepped portions  106  is fitted into the fitting recess  42  of the main body  14 . The main body  14  includes recessed grooves  44  on the inner sides of the pair of wide side surfaces  30 , and the projecting portions  104  of the second porous body  96  are fitted into the recessed grooves  44  (see  FIG.  4   ). By the projecting portions  104  of the second porous body  96  being fitted into the recessed grooves  44  of the main body  14 , the center of the second porous body  96  is prevented from being lifted by being dragged by the drive rod  70  inserted into the first hole portion  100 . 
     The width W 2  of the stepped portions  106  of the second porous body  96  is equal to or slightly larger than the width W 0  of the pivoting portions  82  of the fingers  80 . In the entire pivot range of the fingers  80 , the second curved surfaces  86  of the pivoting portions  82  of the fingers  80  come into contact with corner portions  108  of the stepped portions  106  of the second porous body  96  (see  FIG.  3   ). The portion of the second porous body  96  that comes into contact with each of the second curved surfaces  86  is deformed by being pressed by the second curved surface  86 . 
     As shown in  FIG.  7   , the third porous bodies  110  are formed in an elongated rectangular plate shape. The third porous bodies  110  are attached to the main body  14  so as to face the end surfaces of the pivoting portions  82  of the fingers  80 . As shown in  FIG.  8   , the main body  14  includes fitting grooves  46  on the inner sides of the pair of side walls  28 , and the third porous bodies  110  are fitted into the fitting grooves  46 . The third porous bodies  110  are disposed at four locations in total, correspondingly to the two end surfaces of the pivoting portion  82  of each finger  80 . In the entire pivot range of the fingers  80 , the end surfaces of the pivoting portions  82  of the fingers  80  come into surface contact with the third porous bodies  110  at a predetermined pressure. The third porous bodies  110  each include, at the center thereof in the length direction, a hole portion  112  through which the pivot support shaft  40  is inserted. 
     The main body  14  includes a third port  26  to which purge air is supplied, and a communication passage  27  that allows the third port  26  to communicate with the second hole portion  102  of the second porous body  96  (see  FIG.  3   ). The purge air supplied from the third port  26  passes through the communication passage  27  of the main body  14  and the second hole portion  102  of the second porous body  96 , and enters the purge air storage space  38  to increase the pressure in the purge air storage space  38 . 
     The air filling the purge air storage space  38  passes through the interior of the first to third porous bodies  94 ,  96 , and  110 , and is then discharged to the outside. At this time, the air passes through the surface of the first porous body  94  exposed to the outside between the end plate  48  and the first curved surface  84  of each of the pivoting portions  82  (see  FIGS.  1  and  9   ). Further, air passes through the surface of the second porous body  96  exposed to the outside between the main body  14  and the second curved surface  86  of each of the pivoting portions  82  (see  FIGS.  1  and  9   ). Furthermore, air passes through the surface of the third porous body  110  exposed to the outside between the main body  14  and the end surface of each of the pivoting portions  82  (see  FIG.  1   ). 
     Next, an opening/closing operation of the fulcrum opening/closing type air chuck  10  will be described with reference to  FIGS.  10  and  11   . The fulcrum opening/closing type air chuck  10  is attached to, for example, a conveyance device that conveys a workpiece. As shown in  FIG.  10   , a state in which the pair of fingers  80  are aligned in a straight line is defined as an initial state. 
     The conveyance device (not shown) is driven to convey the fulcrum opening/closing type air chuck  10  to a position where the fulcrum opening/closing type air chuck  10  can grip a workpiece (not shown). Thereafter, a switching valve (not shown) is switched to a predetermined operating position, so that the first port  22  is connected to an air supply source (not shown) and the second port  24  is connected to an exhaust port (not shown). As a result, air is supplied to the first pressure chamber  18 , and air in the second pressure chamber  20  is discharged, whereby the piston  60  and the drive rod  70  move downward. 
     When the drive rod  70  moves downward, the pair of fingers  80  pivot in a direction in which the pair of gripping portions  92  approach each other. The pair of fingers  80  pivot to a position where the pair of gripping portions  92  abut against the end plate  48 , whereby the fulcrum opening/closing type air chuck  10  is brought into a closed state (see  FIG.  11   ), and the workpiece is sandwiched between the pair of fingers  80 . It should be noted that, according to the shape and size of the workpiece, an attachment member (not shown) can be attached to an attachment hole  93  provided in the gripping portion  92 . 
     The conveyance device is driven again to convey the fulcrum opening/closing type air chuck  10  to a place where the fulcrum opening/closing type air chuck  10  releases the workpiece. Thereafter, the switching valve is switched to another operation position, so that the first port  22  is connected to the exhaust port and the second port  24  is connected to the air supply source. As a result, air is supplied to the second pressure chamber  20 , and air in the first pressure chamber  18  is discharged, whereby the piston  60  and the drive rod  70  move upward. When the drive rod  70  moves upward, the pair of fingers  80  pivot in a direction in which the pair of gripping portions  92  move away from each other, and the workpiece is released. The piston  60  moves upward until the damper  68  abuts against the bush  72 , and the pair of fingers  80  are again aligned in a straight line (see  FIG.  10   ). 
     Next, the dust-proof function of the fulcrum opening/closing type air chuck  10  will be described. The purge air storage space  38  is isolated from the outside by the pivoting portions  82  of the fingers  80  and the first to third porous bodies  94 ,  96 , and  110 . External dust that is larger than the voids present inside the first to third porous bodies  94 ,  96 , and  110  cannot enter the interior of the first to third porous bodies  94 ,  96 , and  110  as a matter of course. External dust that is smaller than the voids present inside the first to third porous bodies  94 ,  96 , and  110  cannot enter the interior of the first to third porous bodies  94 ,  96 , and  110  by the supply of the purge air. Hereinafter, the dust-proof action by the supply of the purge air will be described. 
     The third port  26  is constantly connected to an air supply source. That is, the purge air is constantly supplied to the third port  26 . The purge air supplied from the third port  26  enters the purge air storage space  38  to increase the pressure in the purge air storage space  38 . Then, the air filling the purge air storage space  38  passes through the interior of the first to third porous bodies  94 ,  96 , and  110 , and is then discharged to the outside. At this time, the air passes through the surfaces of the first to third porous bodies  94 ,  96 , and  110  exposed to the outside between the body  12  and the pivoting portions  82 . 
     The pressure in the purge air storage space  38  is sufficiently higher than the pressure (atmospheric pressure) on the surfaces of the first to third porous bodies  94 ,  96 , and  110  exposed to the outside. Therefore, external dust that is smaller than the voids present inside the first to third porous bodies  94 ,  96 , and  110  cannot enter the interior of the first to third porous bodies  94 ,  96 , and  110 . Even if fine dust enters the interior of the first to third porous bodies  94 ,  96 , and  110 , the fine dust is discharged to the outside together with the purge air. 
     The fulcrum opening/closing type air chuck  10  according to the present embodiment includes the first porous body  94  that is attached to the end plate  48  and comes into contact with the fingers  80 . Further, the fulcrum opening/closing type air chuck  10  includes the second porous body  96  and the third porous bodies  110  that are attached to the main body  14  and come into contact with the fingers  80 . Furthermore, the purge air passes through the first to third porous bodies  94 ,  96 , and  110  and is discharged to the outside. Therefore, dust can be prevented from entering the interior of the body  12  without increasing the sliding resistance of the fingers  80 . By preventing the entry of the dust, durability of the rod packing  74 , the piston packing  62 , and the like disposed in the cylinder hole  16  is improved. 
     In the present embodiment, the purge air is constantly supplied, but when the fulcrum opening/closing type air chuck  10  is used in an environment where there is little dust outside, the purge air may be intermittently supplied. 
     The fulcrum opening/closing type air chuck according to the present invention is not limited to the embodiment described above, and various configurations may be adopted therein without deviating from the essence and gist of the present invention.