Holding device

Abstract

To provide a gripping device that can stably grip a workpiece with a hole. [Solution] The gripping device 100 according to the present invention is a gripping device attached to a robot 102 for gripping a workpiece 104 with a hole 106, and comprises a base 126, two or more pins 128 erected from the base toward one surface 104a of the workpiece and in contact with the periphery 106a of the hole 106, a shaft 130 provided on the base and inserted into the hole in the workpiece, a plurality of claws 132a, 132b, 132c that expand in diameter at the workpiece-side end 130a of the shaft and in contact with the edge 106b on the other surface 104b side opposite the one surface of the hole in the workpiece, and a cylinder 136 that pulls the shaft toward the base, and the plurality of claws, when the cylinder pulls the shaft, in contact with the edge on the other surface side of the hole in the workpiece and grip the workpiece together with the two or more pins.

Description

Technical Field

[0006]

[0001] The present invention relates to a gripping device that is attached to a robot and grips a workpiece with holes.

Background Art

[0002] As a robot for transporting various workpieces, an articulated robot having a plurality of arms is adopted. The arms are driven by an electric motor or the like provided at each joint thereof to realize a target operation. At the tip of the arm, a robot hand as a gripping device for gripping a workpiece, for example, is attached. Further, as workpieces, there are workpieces with holes and workpieces having unevenness on the surface.

[0003] Patent Document 1 describes an article gripping device that grips a workpiece with holes. The article gripping device has two claws that are attached to the lower part of a cylinder so as to be openable and closable, and protrusions are provided at the tips of the two claws. In the article gripping device, by opening the two claws through the holes of the workpiece, the protrusions of the two claws are hooked on the chamfered portions provided in the holes of the workpiece to grip it.

[0004] As another method, it is conceivable to press three pins against the surface of a workpiece with holes, further penetrate a hook-shaped claw through the hole of the workpiece, pull up the claw and make it abut against the back surface of the workpiece, and grip the workpiece by sandwiching it between the claw and the three pins.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Workpieces transported by robots are fed into processing machines or other equipment in a predetermined orientation. Therefore, gripping devices such as robot hands may need to rotate the workpiece 90° to grip it, or flip it over to grip it. The article gripping device described in Patent Document 1 merely grips the workpiece by hooking the projections of two claws onto the chamfered portion of the hole in the workpiece, and depending on the orientation of the workpiece, it may not be able to grip it stably, as the workpiece may wobble.

[0007] Furthermore, in the method of gripping a workpiece by pressing three pins against its surface and contacting the back surface with claws, it may not be possible to grip the workpiece stably depending on its orientation.

[0008] Specifically, the grip may become unstable if the claws are not positioned within the triangle formed by the three pins, or the workpiece may wobble if only two of the three pins are in contact with the workpiece surface. In particular, if the workpiece wobbles, the remaining pin that is not in contact with the workpiece surface may repeatedly collide with the workpiece surface, causing indentations. Furthermore, since the two pins that are in contact with the workpiece surface are making contact at an angle, the two pins may dig into the workpiece surface, causing scratches.

[0009] In view of these problems, the present invention aims to provide a gripping device that can stably grip a workpiece with a hole. [Means for solving the problem]

[0010] To solve the above problems, a typical configuration of the gripping device according to the present invention is a gripping device that is attached to a robot and grips a workpiece with a hole, comprising: a base; two or more pins erected from the base toward one surface of the workpiece and in contact with the periphery of the hole; a shaft provided on the base and inserted into the hole of the workpiece; a plurality of claws that expand in diameter at the workpiece-side end of the shaft and in contact with the edge of the other side of the hole facing the one surface of the hole in the workpiece; and a cylinder that pulls the shaft toward the base, wherein the plurality of claws, as the cylinder pulls the shaft, in contact with the edge of the other side of the hole in the workpiece and grip the workpiece together with the two or more pins.

[0011] Preferably, the two or more pins and the plurality of claws are arranged such that at least one of the straight lines connecting two of the two or more pins intersects with one of the straight lines connecting two of the plurality of claws.

[0012] Preferably, there are three or more pins, and one or more claws are located inside the polygon formed by connecting the three or more pins.

[0013] Preferably, there are three of the multiple claws mentioned above.

[0014] Preferably, the above-mentioned multiple claws are attached, and the shaft is equipped with multiple claw pivot shafts extending substantially parallel to the axial direction of the shaft, and the multiple claws expand in diameter by protruding from the outer surface of the shaft or contract in diameter by being housed inside the shaft as the multiple claw pivot shafts rotate.

[0015] The system comprises a rotating actuator which is a driving force source for expanding or contracting the diameter of the multiple claws described above, one or more drive gears attached to the output shaft of the rotating actuator, and multiple claw-side gears attached to each of the multiple claw rotation shafts and meshing with one or more of the drive gears, wherein the gear ratio of the claw-side gear of at least one claw and the drive gear meshing with it is preferably different from the gear ratio of the other claws. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a gripping device that can stably grip a workpiece with holes.

Brief Description of the Drawings

[0017] [Figure 1] It is a diagram for explaining an overview of a robot to which the gripping device in an embodiment of the present invention is applied. [Figure 2] It is a perspective view showing a main part of the gripping device of FIG. 1. [Figure 3] It is a partially enlarged perspective view for explaining a mechanism for opening and closing the claws of the gripping device of FIG. 2. [Figure 4] It is a partial perspective view of the gripping device of FIG. 3 viewed from another direction. [Figure 5] It is a diagram for explaining the opening angle of the claws of the gripping device of FIG. 2. [Figure 6] It is a diagram for explaining the operation of the gripping device of FIG. 1 for gripping a workpiece. [Figure 7] It is a diagram showing a state where the gripping device of FIG. 1 is gripping a workpiece. [Figure 8] It is a diagram showing a state where the claws of the gripping device are in contact with the edge on the back side of the hole of the workpiece. [Figure 9] It is a schematic diagram showing the arrangement relationship between the claws and pins of the gripping device. [Figure 10] It is a diagram showing a state where the gripping device of the comparative example (conventional structure) is gripping a workpiece.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Dimensions, materials, and other specific numerical values shown in such embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals to omit redundant explanations, and elements not directly related to the present invention are not shown.

[0019] Figure 1 is a diagram illustrating the outline of a robot 102 to which a gripping device 100 in an embodiment of the present invention is applied, along with a workpiece 104. The gripping device 100 is a manipulator attached to the robot 102 that grips a workpiece 104 with a hole. The workpiece 104 gripped by the gripping device 100 is transported by the robot 102 and fed into a processing machine or the like in a predetermined position. In the figure, the gripping device 100 is exemplified as a robot hand, and the workpiece 104 with a hole is exemplified as a transmission case having a hole 106.

[0020] Robot 102 is, for example, a 7-axis articulated robot and comprises a base 110 installed on the floor 108 of a factory or the like, a swivel frame 112, a first arm 114, a lower connecting arm 116, an upper connecting arm 118, a second arm 120, and a joint 122.

[0021] The slewing frame 112 rotates on the J1 axis. The J1 axis is supported in a direction approximately perpendicular to the floor 108 when the base 110 is installed on the floor 108. The first arm 114 rotates on the J2 axis. The J2 axis is supported by the slewing frame 112 in a direction approximately perpendicular to the J1 axis.

[0022] The lower connecting arm 116 is rotatably connected to the first arm 114 via a J3 axis that extends longitudinally from the first arm 114, allowing it to twist around the J3 axis. The upper connecting arm 118 is rotatably connected to the lower connecting arm 116 via a J4 axis. The J4 axis is supported on the lower connecting arm 116 substantially parallel to the J2 axis. The second arm 120 is rotatably connected to the upper connecting arm 118 via a J5 axis that extends longitudinally from the second arm 120, allowing it to twist around the J5 axis.

[0023] Joint 122 is attached to the tip 124 of the second arm 120 and rotates relative to the second arm 120 in a tilting direction rather than a twisting direction via the J6 axis. A gripping device 100 is attached to joint 122. The gripping device 100 rotates via the J7 axis in a direction approximately perpendicular to the rotation direction of joint 122 (twisting direction). The J6 and J7 axes are also supported by joint 122 in a direction approximately perpendicular to the J5 axis. It should be noted that the configuration of robot 102 shown in Figure 1 is merely an example and is not limited to this configuration.

[0024] Figure 2 is a perspective view showing the main parts of the gripping device 100 shown in Figure 1. Figures 2(a) and (b) show the gripping device 100 viewed from diagonally above and diagonally below, respectively. The robot 100 has a plate-shaped base 126, a plurality of pins 128, a shaft 130, a plurality of claws 132, a rotating actuator 134, and a cylinder 136.

[0025] The base 126 is attached to the joint 122 of the robot 102 shown in Figure 1 via a connecting portion 137. The pins 128 are erected from the base 126 toward one surface of the workpiece 104 shown in Figure 7 (in this case, the surface 104a) and abut against the periphery of the hole 106. There are at least three pins 128, and in a state where they abut against the periphery 106a of the hole 106 of the workpiece 104 shown in Figure 7, it is possible to support the surface 104a of the workpiece 104 at three or more points.

[0026] Furthermore, a length-adjusting screw 128a is attached to the tip of the pin 128. This allows the operator to adjust the length of the pin 128 by adjusting the screw 128a to match the surface 104a of the workpiece 104, even if there are irregularities on the surface 104a of the workpiece 104. This ensures that the pin 128 reliably supports the surface 104a of the workpiece 104 at three or more points.

[0027] The shaft 130 is mounted on the base 126 and is inserted into the hole 106 of the workpiece 104 when the gripping device 100 grips the workpiece 104. The claws 132 include three claws 132a, 132b, and 132c. As shown in Figure 2, the claws 132a, 132b, and 132c protrude from the outer circumferential surface 130c of the cover 130b of the shaft 130 at the end of the shaft 130 on the workpiece 104 side (hereinafter referred to as the tip 130a), expanding in diameter, or retracting into the inside of the shaft 130 to reduce in diameter. In other words, each claw 132a to 132c is a member that can be expanded and contracted (opened and closed).

[0028] The rotary actuator 134 is a driving force source that opens and closes the claws 132a, 132b, and 132c to expand or contract their diameter. The rotary actuator 134 has a drive shaft (output shaft 138) as shown in Figure 3, and the output shaft 138 can be rotated in both forward and reverse directions. The rotary actuator 134 can use, for example, a mechanical rotor that rotates by a predetermined angle using air as a driving source, but a solenoid or a stepping motor may also be used.

[0029] The cylinder 136 has a rod 140 as shown in Figure 2(b), to which a shaft 130, a claw 132, and a rotary actuator 134 are attached. Therefore, by moving the rod 140 toward the base 126, the shaft 130, claw 132, and rotary actuator 134 are all pulled toward the base 126. The cylinder 136 can preferably be an air cylinder, for example.

[0030] Figure 3 is a partially enlarged perspective view illustrating the mechanism for opening and closing the claws 132 of the gripping device 100 shown in Figure 2. Figure 4 is a partially perspective view of the gripping device 100 shown in Figure 3 from a different direction. Note that in the figure, the cover 130b of the shaft 130 has been removed to show the internal structure of the shaft 130.

[0031] The output shaft 138 of the rotary actuator 134 is housed inside the shaft 130 (see Figure 2). Two drive gears 142 and 144 with different numbers of teeth are arranged on the output shaft 138, spaced apart in the axial direction. Furthermore, several (in this case, three) pawl rotation shafts 146a, 146b, and 146c, which are housed inside the shaft 130, are arranged around the output shaft 138.

[0032] The pawl pivot shafts 146a, 146b, and 146c extend approximately parallel to the axial direction of the shaft 130, and pawls 132a, 132b, and 132c are attached to them, respectively. The pawls 132a, 132b, and 132c are located near the tip 130a of the shaft 130, as shown in the figure.

[0033] The same number of teeth are attached to the pawl pivot shafts 146a and 146b, respectively. Both pawl gears 148a and 148b mesh with the drive gear 142 of the output shaft 138, as shown in the figure. The pawl pivot shaft 146c is fitted with a pawl gear 148c that meshes with the drive gear 144 of the output shaft 138. The number of teeth of pawl gear 148c is different from that of pawl gears 148a and 148b.

[0034] Therefore, when the drive gears 142 and 144 rotate together with the output shaft 138 of the rotary actuator 134, the pawl rotation shafts 146a, 146b, and 146c, to which the pawl-side gears 148a, 148b, and 148c that mesh with them are attached, also rotate. As a result, the pawls 132a, 132b, and 132c attached to the pawl rotation shafts 146a, 146b, and 146c protrude from the outer circumferential surface 130c (see Figure 2) of the cover 130b of the shaft 130, expanding in diameter, or are housed inside the shaft 130, reducing in diameter.

[0035] Here, drive gear 144 has more teeth than drive gear 142. Also, pawl-side gear 148c has fewer teeth than pawl-side gears 148a and 148b. As a result, the gear ratio between pawl-side gears 148a and 148b and the drive gear 142 that meshes with them is large, and the opening angle of pawls 132a and 132b is large. The gear ratio between pawl-side gear 148c and the drive gear 144 that meshes with it is small, and the opening angle of pawl 132c is small.

[0036] Figure 5 illustrates the opening angles of the claws 132a, 132b, and 132c of the gripping device 100 shown in Figure 2. Figures 5(a) and 5(b) show the claws 132a, 132b, and 132c in a reduced diameter state and an expanded diameter state, respectively.

[0037] The opening angle when expanding the diameter of the claws 132a, 132b, and 132c is appropriately set by the gear ratio between the claw-side gears 148a, 148b, and 148c and the drive gears 142 and 144 that mesh with them. In the gripping device 100, the gear ratios of the claws 132a, 132b and the claw 132c are different, so the opening angles of the claws 132a, 132b and the claw 132c can be made different.

[0038] Specifically, the pawls 132a and 132b have the same gear ratio. Therefore, the pawls 132a and 132b, which are housed inside the shaft 130 and have a reduced diameter (see Figure 5(a)), rotate 120° and expand in diameter as the pawl pivot shafts 146a and 146b rotate, as illustrated in Figure 5(b).

[0039] On the other hand, because the gear ratio of pawl 132c is smaller than that of pawls 132a and 132b, pawl 132c rotates 90° from the reduced diameter state shown in Figure 5(a) to the expanded diameter state shown in Figure 5(b) as the pawl pivot shaft 146c rotates. Note that the opening angles of 120° and 90° for pawls 132a, 132b, and 132c are merely examples, and the opening angles can be set appropriately according to the gear ratio.

[0040] In this way, the gripping device 100 can expand or contract the claws 132a, 132b, and 132c at the tip 130a of the shaft 130 simply by rotating the claw rotation axes 146a, 146b, and 146c. Furthermore, by changing the gear ratio, the opening angles of the claws 132a, 132b and claw 132c can be made different.

[0041] Figure 6 illustrates the operation of the gripping device 100 in Figure 1 in gripping the workpiece 104. Figure 7 shows the state in which the gripping device 100 in Figure 1 is gripping the workpiece 104. Note that Figure 7 shows the cross-sectional shape of the workpiece 104.

[0042] First, the robot 102 (see Figure 1) is moved to bring three or more pins 128 into contact with the area 106a around the hole 106 on the surface 104a of the workpiece 104 shown in Figure 7, and then the shaft 130 is inserted into the hole 106 of the workpiece 104 as shown in Figure 6(a). At this time, the claws 132 are housed inside the shaft 130 and their diameter is reduced. Also, the cylinder 136 has its rod 140 protruding, moving the shaft 130 away from the base 126.

[0043] Next, the rotating actuator 134 (see Figure 2) expands the diameter of the claws 132a, 132b, and 132c at the tip 130a of the shaft 130, as shown in Figure 6(b), so that they face the edge 106b of the hole 106 of the workpiece 104. The edge 106b of the hole 106 of the workpiece 104 is the edge on the other side (in this case, the back surface 104b) that faces one side (the front surface 104a) of the hole 106 of the workpiece 104.

[0044] Next, as shown in Figure 6(c), the cylinder 136 (see Figure 2) pulls the shaft 130 closer, biasing the claws 132a, 132b, and 132c to contact the edge 106b of the hole 106 in the workpiece 104.

[0045] As a result, as shown in Figure 7, the pin 128 enables three-point support of the surface 104a of the workpiece 104, and the three claws 132a, 132b, and 132c further enable three-point support of the back surface 104b of the workpiece 104. Therefore, with the gripping device 100, the workpiece 104 can be gripped on both sides by at least three pins 128 and three claws 132a, 132b, and 132c, thus enabling stable gripping of the workpiece 104 with holes.

[0046] However, in order to stably grip the workpiece 104, it is sufficient that at least one of the three claws 132a, 132b, and 132c be located inside the triangle formed by connecting the pins 128 that support the surface 104a of the workpiece 104 with straight lines. For this reason, the gripping device 100 includes three claws 132a, 132b, and 132c, but is not limited to this, and may have only two claws. That is, even with only two claws, at least one claw is located inside the triangle formed by connecting the pins 128, so the workpiece 104 can be gripped stably by clamping it with multiple (two or more) claws and three or more pins 128.

[0047] Figure 10 shows a gripping device 200 of a comparative example (conventional structure) gripping a workpiece 202. The gripping device 200 comprises three pins 204 and hook-shaped claws 206.

[0048] When gripping a workpiece 202 with a hole, the gripping device 200 presses three pins 204 against the surface 202a of the workpiece 202, as shown in Figure 10(a), and then penetrates the hole 208 of the workpiece 202 with its claws 206.

[0049] Next, the gripping device 200 lifts the claws 206 and brings them into contact with the back surface 202b of the workpiece 202, thereby gripping the workpiece 202 by sandwiching it between the claws 206 and the three pins 204.

[0050] However, with the gripping device 200, there are cases where the workpiece 202 is gripped in an unstable manner, such as when the claws 206 are not positioned inside the triangle formed by the three pins 204, or when the claws 206 rest on the sides of the triangle. In addition, there are cases where only two of the three pins 204 contact the surface 202a of the workpiece 202, causing the workpiece 202 to wobble.

[0051] In particular, if the workpiece 202 becomes unstable, the remaining pin 204 that is not in contact with the surface 202a of the workpiece 202 may repeatedly collide with the surface 202a of the workpiece 202, causing indentations. Furthermore, since the two contacting pins 204 are also in contact with the surface 202a of the workpiece 202 at an angle, the two pins 204 may dig into the surface 202a of the workpiece 202, causing scratches.

[0052] In contrast, the gripping device 100 in this embodiment can grip the workpiece 104 on both sides using at least three pins 128 and multiple (two or more) claws 132, as described above, thus enabling stable gripping of the workpiece 104 with holes.

[0053] Figure 8 shows the state in which the claws 132a, 132b, and 132c of the gripping device 100 are in contact with the edge 106b on the back surface 104b side of the hole 106 of the workpiece 104. As described above, the gripping device 100 has different gear ratios for the claws 132a, 132b and the claw 132c, so that the opening angles can be made different when the diameter is expanded. As an example, as shown in Figure 5(c), the opening angles of the claws 132a, 132b and the claw 132c are 120° and 90°, respectively.

[0054] Therefore, even if protrusions 150a, 150b, 150c, and 150d are present on the back surface 104b side edge 106b of the hole 106 of the workpiece 104, the claws 132a, 132b, and 132c can be reliably brought into contact with the back surface 104b side edge 106b of the hole 106 of the workpiece 104, avoiding the protrusions 150a, 150b, 150c, and 150d.

[0055] As a result, the gripping device 100 prevents the surface gripping of the back surface 104b of the workpiece 104 by the three claws 132a, 132b, and 132c from tilting, and allows for stable gripping of the workpiece 104 from both sides.

[0056] Figure 9 is a schematic diagram showing the arrangement of the claws 132a, 132b, and 132c and the pin 128 of the gripping device 100. The gripping device 100 can stably grip the workpiece 104 even if the arrangement of the claws 132a, 132b, and 132c and the pin 128 is changed as appropriate.

[0057] Specifically, as shown in Figure 9(a), three enlarged claws 132a, 132b, and 132c facing the edge 106b of the hole 106 in the workpiece 104 may be positioned inside a triangle A formed by connecting the pins 128 that support the surface 104a of the workpiece 104 with straight lines. With such an arrangement, if there are three or more pins 128, the pins 128 will form a surface, and the three claws 132a, 132b, and 132c will also form a surface, so the workpiece 104 can be gripped stably.

[0058] As shown in Figure 9(b), one claw (for example, claw 132c) may be positioned inside the triangle A formed by connecting the pins 128 with straight lines. With this arrangement, the workpiece 104 can be held stably by clamping it with one claw 132c and three or more pins 128. Alternatively, any two of the three claws 132a, 132b, and 132c may be positioned inside the triangle A formed by connecting the pins 128. Even with this arrangement, the workpiece 104 can be held stably by clamping it with two claws and three or more pins 128.

[0059] Furthermore, the number of pins 128 is not limited to three or more; it may be two or more. Specifically, as shown in Figure 9(c), two pins 128 and three claws 132a, 132b, and 132c may be arranged such that the line B connecting the two pins 128 passes through the triangle F formed by lines C, D, and E connecting the three claws 132a, 132b, and 132c. Note that line B intersects lines C and E. With this arrangement, the three claws 132a, 132b, and 132c form a surface, and the two pins 128 act as stopper positions, so the workpiece 104 can be gripped and held stably.

[0060] Furthermore, as shown in Figure 9(d), the straight line B connecting the two pins 128 may be arranged to intersect with the straight line (here, straight line C) connecting any two of the three claws 132a, 132b, and 132c (here, claws 132a and 132b). With this arrangement, the two pins 128 suppress rotation of the workpiece 104 around the axis of straight line B, and the two claws 132a and 132b suppress rotation of the workpiece 104 around the axis of straight line C, thereby gripping the workpiece 104 and holding it stably.

[0061] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these examples. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. [Industrial applicability]

[0062] This invention can be used as a gripping device that can be attached to a robot to grip a workpiece with holes. [Explanation of symbols]

[0063] 100...Gripping device, 102...Robot, 104...Workpiece, 104a...One side (front) of the workpiece, 104b...Other side (back) of the workpiece, 106...Hole in the workpiece, 106a...Perimeter of the hole, 106b...Edge on the back side of the hole, 108...Floor, 110...Base, 112...Swivel frame, 114...First arm, 116...Lower connecting arm, 118...Upper connecting arm, 120...Second arm, 122...Joint, 124...Tip of the second arm, 126...Base, 128...Pin, 128a...Screw on the pin, 130...Shaft T, 130a... Shaft end (tip) on the workpiece side, 130b... Shaft cover, 130c... Outer circumference of the shaft, 132, 132a, 132b, 132c... Claw, 134... Rotary actuator, 136... Cylinder, 137... Base connecting part, 138... Output shaft of the rotary actuator, 140... Cylinder rod, 142, 144... Drive gear, 146a, 146b, 146c... Claw rotation shaft, 148a, 148b, 148c... Claw-side gear, 150a, 150b, 150c, 150d... Protrusion

Claims

1. In a gripping device attached to a robot for gripping a workpiece with a hole, Bass and, Two or more pins are erected from the base toward one surface of the workpiece and abut the periphery of the hole, A shaft provided on the base is inserted into the hole in the workpiece, The shaft has a diameter that expands at the end on the workpiece side, and has a plurality of claws that contact the edge on the other side of the hole in the workpiece that is opposite to one side, The system includes a cylinder that pulls the shaft towards the base, A gripping device characterized in that the plurality of claws contact the edge on the other side of the hole in the workpiece when the cylinder pulls the shaft, and together with the two or more pins, grip the workpiece.

2. The two or more pins and the multiple claws are, The gripping device according to claim 1, characterized in that at least one of the two or more pins is arranged such that it intersects with one of the lines connecting two of the multiple claws.

3. The aforementioned pins are three or more. The gripping device according to claim 1, characterized in that one or more claws are located inside a polygon formed by connecting the three or more pins.

4. The gripping device according to claim 1, characterized in that the plurality of claws are three.

5. The aforementioned multiple claws are attached to a plurality of claw pivot shafts that extend substantially parallel to the axial direction of the shaft, The gripping device according to claim 1, characterized in that the plurality of claws expand in diameter by protruding from the outer surface of the shaft or contract in diameter by being housed inside the shaft as the plurality of claw pivot shafts rotate.

6. A rotation actuator, which is a driving force source for expanding or contracting the diameter of the plurality of claws, One or more drive gears attached to the output shaft of the aforementioned rotary actuator, Each of the aforementioned plurality of pawl pivot shafts is attached to a plurality of pawl-side gears that mesh with one or more of the aforementioned drive gears, The gripping device according to claim 5, characterized in that the gear ratio between the claw-side gear of at least one claw and the drive gear that meshes with it is different from the gear ratio of the other claws.

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