Gripper Device

Abstract

To provide a gripper device reduced in size while having a sufficient stroke.SOLUTION: A gripper device 10 includes: an air cylinder 12 having a piston rod 18; a rotation output mechanism 20 having a screw shaft 22 and a nut 24 and configured to convert a rectilinear motion of the piston rod 18 into a rotational motion; a plurality of linear motion parts 62 to each of which a gripper claw 60 is connected; and a rectilinear output mechanism 40 configured to convert a rotational motion output from the rotation output mechanism 20 into a linear motion and transmit the linear motion to the plurality of linear motion parts 62, the rectilinear, the rectilinear output mechanism 40 having a pinion gear 42 and a rack gear 48; wherein the nut 24 is disposed on an inner-diameter side of the pinion gear 42, and a rectilinear stroke of the rectilinear motion part 62 is larger than a rectilinear stroke of the piston rod 18.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present specification discloses a gripper device that holds an object with multiple gripper jaws. [Background technology]

[0002] Gripper devices that hold an object by moving multiple gripper claws forward and backward in a straight line have been known for some time. Such gripper devices are, for example, attached to robots as end effectors or installed in the processing chambers of machine tools.

[0003] In addition, it has been widely proposed to use an air cylinder as a power source for moving the gripper claws back and forth. However, if a long-stroke air cylinder is used to increase the stroke of the gripper claws, there is a problem that the entire gripper device becomes large.

[0004] Therefore, some have proposed a technique for increasing the stroke of the gripper claws by providing multiple gears between the air cylinder and the gripper claws. For example, Patent Document 1 discloses a chuck device in which a pair of finger bodies (corresponding to the gripper claws) is advanced and retreated by an air cylinder. In Patent Document 1, a rack gear is formed on the piston of the air cylinder, and this rack gear meshes with a driven pinion gear. The driven pinion gear is connected to the driven pinion gear via a driven shaft. The driven pinion gear further meshes with driven rack gears provided on the pair of finger bodies. In this case, the driven pinion gear and the driven pinion gear rotate as the piston advances and retreats, thereby moving the driven rack gear and the finger bodies forward and backward in a straight line. Patent Document 1 also describes that if the pitch diameter of the driven pinion gear is made larger than that of the driven pinion gear, the opening and closing stroke of the finger bodies can be ensured to be longer than the stroke of the air cylinder. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 3-82185 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology of Patent Document 1 was unable to sufficiently reduce the size of the gripper device. That is, in the configuration of Patent Document 1, the drive pinion gear that converts the linear motion of the piston into rotational motion and the driven pinion gear that transmits the rotational motion to the driven rack gear are arranged with a large offset in the direction of their rotation axes. Here, the rotation axes of the drive pinion gear and the driven rack gear are parallel to the thickness direction of the chuck device. Therefore, the configuration of Patent Document 1 tends to make the dimension of the chuck device in the thickness direction large.

[0007] Therefore, this specification discloses a gripper device that has a sufficient stroke but is small in size. [Means for solving the problem]

[0008] The gripper device disclosed in this specification includes: an air cylinder having a piston rod that advances and retreats linearly; a screw shaft fixed to the piston rod; and a nut screwed onto the screw shaft, the rotation output mechanism converting the linear motion of the piston rod into rotational motion; a plurality of linear motion parts that advance and retreat in synchronization with each other, each having a gripper claw connected to it; and a linear motion output mechanism that converts the rotational motion output from the rotation output mechanism into linear motion and transmits it to the plurality of linear motion parts, the linear motion output mechanism having a pinion gear that rotates in synchronization with the nut and a rack gear that meshes with the pinion gear, the nut being disposed on the inner diameter side of the pinion gear, and the linear motion stroke of the linear motion part being greater than the linear stroke of the piston rod. and an axial range of the nut overlaps with at least a portion of an axial range of the pinion gear. It is characterized by:

[0009] With this configuration, a sufficient stroke can be ensured for the gripper claws by adjusting the lead of the screw shaft and the pitch circle diameter of the pinion gear, etc. Also, because the nut is disposed on the inner diameter side of the pinion gear, the size of the gripper device, particularly the dimension in the thickness direction of the gripper device (i.e., the direction perpendicular to the opening and closing direction of the gripper claws), can be reduced.

[0010] In this case, when the module of the pinion gear is m, the number of teeth of the pinion gear is z, and the lead of the screw shaft is R, (π·m·z / R)>1 may be satisfied.

[0011] With this configuration, the linear stroke of the linear moving part can be reliably made larger than the linear stroke of the piston rod.

[0012] In addition, the axial direction of the piston rod, the axial direction of the screw shaft, the axial direction of the nut, and the rotational axis direction of the pinion gear may be parallel, the axial direction of the piston rod is perpendicular to the linear direction of the multiple linear motion parts, the axial range of the piston rod overlaps with at least a portion of the axial range of the screw shaft, and the axial range of the screw shaft overlaps with at least a portion of the axial range of the pinion gear.

[0013] With this configuration, the dimension of the gripper device in the thickness direction can be further reduced. [Effects of the Invention]

[0014] The gripper device disclosed in this specification can have a sufficient stroke while being small in size. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a perspective view of the gripper device in a closed state. [Figure 2] FIG. 2 is a perspective view of the gripper device in an open state. [Figure 3] FIG. 1 is a perspective view of a gripper device with a case and a protective cover removed; [Figure 4] FIG. 2 is a cross-sectional view of the gripper device in a closed state. [Figure 5] FIG. 2 is a cross-sectional view of the gripper device in an open state. [Figure 6] 5 is a cross-sectional view taken along the line AA in FIG. 4. [Figure 7] 6 is a cross-sectional view of FIG. 5 taken along line B-B. [Figure 8] FIG. 10 is a diagram showing how workpieces are stacked using a gripper device. DETAILED DESCRIPTION OF THE INVENTION

[0016] The configuration of the gripper device 10 will be described below with reference to the drawings. Fig. 1 is a perspective view of the gripper device 10 in a closed state, and Fig. 2 is a perspective view of the gripper device 10 in an open state. Fig. 3 is a perspective view of the gripper device 10 with the case 28 and protective cover 52 removed. Figs. 4 and 5 are cross-sectional views of the gripper device 10, Fig. 6 is a cross-sectional view taken along line AA in Fig. 4, and Fig. 7 is a cross-sectional view taken along line BB in Fig. 5.

[0017] The gripper device 10 of this example has three gripper jaws 60 arranged at 120-degree intervals, and holds an object by moving the three gripper jaws 60 back and forth in a straight line relative to one another. Note that, hereinafter, the direction in which the gripper jaws 60 move back and forth is referred to as the "jaw opening / closing direction," and the direction perpendicular to the direction in which the three gripper jaws 60 move back and forth is referred to as the "thickness direction" of the gripper jaws 60. Such a gripper device 10 is, for example, attached to an articulated robot as an end effector, or attached to an actuator in a machine tool for transporting tools and workpieces.

[0018] To move the three gripper jaws 60, the gripper device 10 has an air cylinder 12, a rotation output mechanism 20, a linear output mechanism 40, and a linear motion unit 62. The air cylinder 12 is a power source that moves the gripper jaws 60. As shown in FIGS. 4 and 5 , the air cylinder 12 has a cylinder tube 14, a piston 16 that moves linearly back and forth within the cylinder tube 14, and a piston rod 18 that protrudes from the piston 16 to the outside of the cylinder tube 14. As with a typical air cylinder 12, the piston 16 and the piston rod 18 move linearly back and forth by supplying air to or discharging air from the cylinder tube 14.

[0019] The advancing and retreating direction of the piston rod 18 (i.e., the axial direction of the piston rod 18) is perpendicular to the advancing and retreating direction of the gripper claws 60 (and therefore the axial direction of the linear motion portion 62). In other words, the advancing and retreating direction of the piston rod 18 is parallel to the thickness direction of the gripper device 10.

[0020] A connecting portion 70 is fixed to the circumferential surface of the cylinder tube 14. The connecting portion 70 is a portion that is connected to a robot or an actuator. A general joint mechanism is provided in the connecting portion 70. An engagement groove 72 is formed in the upper portion of the connecting portion 70 and is used to hang and hold the gripper device 10 that has been removed from the robot or the like.

[0021] The rotation output mechanism 20 converts the linear motion of the piston rod 18 into rotational motion. The rotation output mechanism 20 has a screw shaft 22 and a nut 24. The screw shaft 22 is a shaft member with a male thread formed on its outer circumferential surface. A hole is formed in the screw shaft 22 that passes through in the axial direction, and the end of the piston rod 18 is inserted into this hole and fixed. Therefore, the axial direction of the screw shaft 22 is parallel to the axial direction of the piston rod 18, and the screw shaft 22 moves forward and backward in a linear manner together with the piston rod 18.

[0022] A detent 26 is fixed to this screw shaft 22. The outer peripheral surface of the detent 26 has multiple protrusions (not shown) that protrude radially outward, and grooves (not shown) that receive these protrusions are formed on the inner surface of the case 28. In other words, the detent 26 engages with the inner surface of the case 28 in the circumferential direction. This allows the detent 26 and screw shaft 22 to move back and forth in the axial direction, but prevents them from rotating.

[0023] A nut 24 is threaded onto the male thread of the screw shaft 22. The nut 24 is connected to the pinion gear 42 by a connecting bolt 44, and the pinion gear 42 is rotatably supported with respect to the protective cover 52 by a bearing 46. Therefore, while the nut 24 is rotatable, it is prohibited from moving in the axial direction. Therefore, when the screw shaft 22 moves linearly forward and backward in the axial direction, the nut 24 rotates without moving axially. In other words, the nut 24 converts the linear movement of the piston rod 18 into rotational movement.

[0024] The linear output mechanism 40 converts the rotational motion output from the rotational output mechanism 20 into linear motion and transmits it to the three linear motion parts 62. The linear output mechanism 40 has one pinion gear 42 and three rack gears 48. As described above, the pinion gear 42 is a gear that is connected to the nut 24 and rotates together with the nut 24. A hole that penetrates the center of the pinion gear 42 in the axial direction is formed, and the nut 24, the screw shaft 22, and a portion of the piston rod 18 enter this hole. From another perspective, the nut 24 is disposed on the inner diameter side of the pinion gear 42.

[0025] As shown in Figures 6 and 7, three linear motion parts 62 are arranged around the pinion gear 42 at 120-degree intervals. Each linear motion part 62 is a shaft-shaped member, and a rack gear 48 extending in the axial direction of the linear motion part 62 is formed on the peripheral surface of the base end of the shaft. The pinion gear 42 is in mesh with the rack gear 48. Therefore, when the pinion gear 42 rotates, the rack gear 48, and therefore the linear motion part 62, moves linearly forward and backward in the tangential direction of the pinion gear 42 (in other words, the claw opening and closing direction). Note that a guide hole 54 into which the linear motion part 62 is inserted is formed inside the protective cover 52. The linear motion part 62 moves linearly forward and backward while being guided by the guide hole 54.

[0026] Gripper claws 60 are attached to the end of the linear motion portion 62 (i.e., the end opposite the rack gear 48). Therefore, when the piston rod 18 moves linearly back and forth, the nut 24 and pinion gear 42 rotate, and the linear motion portion 62 and gripper claws 60 move linearly back and forth.

[0027] As is clear from the above description, in this example, the air cylinder 12 is used as a power source for moving the gripper claws 60. In this case, the gripper device 10 can be attached to and detached from a robot or actuator more easily than with an electric or hydraulic power source. That is, the gripper device 10 of this example is intended for use in the machining chamber of a machine tool, where cutting water and chips are usually present. Therefore, when an electric type is used, there is a risk that the electrical contacts will be short-circuited or corroded by the cutting water. Furthermore, with a hydraulic type, there is a risk that hydraulic oil will leak or air will get into the hydraulic circuit. On the other hand, with a pneumatic type using the air cylinder 12, these problems do not occur, and the pneumatic circuit can be easily connected.

[0028] Furthermore, a single machine tool typically handles workpieces of various sizes. Even the same workpiece undergoes significant changes in shape from the raw material state before machining to the finished product state after machining. Therefore, the gripper device 10 used with the machine tool is required to have a large stroke. Therefore, in this example, the lead pitch of the screw and the module of the pinion are adjusted to make the linear stroke of the linear portion longer than the linear stroke of the piston rod 18.

[0029] Specifically, if the linear stroke of the piston rod 18 is S and the lead of the screw shaft 22 is R, the rotation angle θn of the nut 24 is θn = 2 π S / R. On the other hand, if the module of the pinion gear 42 is m and the number of teeth of the pinion gear 42 is z, the linear stroke L of the linear motion part 62 is L = m z θn / 2 = π m z S / R. Therefore, to make L > S, it is necessary to make (π m z S / R) > S, and ultimately (π m z / R) > 1.

[0030] Note that (m·z) is the pitch circle diameter of the pinion gear 42. Therefore, for example, if it is desired to increase the stroke of the gripper claws 60 without changing the stroke S of the piston rod 18, the lead R of the screw shaft 22 can be reduced or the pitch circle diameter of the pinion gear 42 can be increased. Note that if the module m is small, even if the pitch circle diameter is increased, it is possible to keep the increase in size of the pinion gear 42, and therefore the increase in size of the gripper device 10, to a minimum.

[0031] The gripper device 10 is also required to be compact. In particular, when the gripper device 10 is used in the machining chamber of a machine tool, if the size of the gripper device 10 is large, the gripper device 10 may interfere with other components such as the spindle or tool post. Furthermore, if the thickness dimension of the gripper device 10 is large, the work of stacking workpieces is limited. This will be described with reference to FIG. 8.

[0032] In a machine tool, a robot 100 may be used to stack multiple workpieces 110, as shown in Fig. 8. In this case, the multiple workpieces 110 are stacked in their thickness direction. A gripper device 10 is attached to the robot 100, and the gripper device 10 grips the workpiece 110 in an orientation in which the thickness direction of the gripper device 10 and the thickness direction of the workpiece 110 are approximately parallel.

[0033] 8, the gripper claws 60 of the gripper device 10b, which has a smaller thickness dimension, can be positioned higher in the stacking direction than the gripper device 10a, which has a larger thickness dimension. Therefore, the smaller the thickness dimension of the workpieces 110, the greater the number of workpieces 110 that can be stacked.

[0034] In this example, in order to reduce the thickness dimension of the gripper device 10, the nut 24 is disposed on the inner diameter side of the pinion gear 42. From another perspective, in this example, the axial range of the nut 24 overlaps with at least a portion of the axial range of the pinion gear 42. Because the axial directions of the nut 24 and the pinion gear 42 are parallel to the thickness direction, overlapping the axial ranges of the two can reduce the thickness dimension of the gripper device 10. Furthermore, in this example, the axial range of the piston rod 18 overlaps with at least a portion of the axial range of the screw shaft 22, and the axial range of the screw shaft 22 overlaps with at least a portion of the axial range of the pinion gear 42. This allows the thickness dimension of the gripper device 10 to be further reduced.

[0035] The configuration described above is merely an example and may be modified as appropriate. For example, the number of gripper claws 60 may be two, four, or more. The shape of the gripper claws 60 may also be modified as appropriate. In this example, the piston rod 18 and the threaded shaft 22 are separate components, but they may be integrated. That is, a male thread functioning as the threaded shaft 22 may be formed at the end of the piston rod 18. However, in this case, a dedicated piston rod 18 must be manufactured. Therefore, when using a general-purpose air cylinder 12, the piston rod 18 and the threaded shaft 22 may be separate components. This configuration makes it easy to replace the air cylinder 12 with one having a different tube diameter depending on the purpose, and the gripping force of the gripper device 10 can be easily changed. Furthermore, the nut 24 and the pinion gear 42 do not need to be separate components; teeth functioning as the pinion gear 42 may be formed on the outer circumferential surface of the nut 24. [Explanation of symbols]

[0036] 10 Gripper device, 12 Air cylinder, 14 Cylinder tube, 16 Piston, 18 Piston rod, 20 Rotation output mechanism, 22 Screw shaft, 24 Nut, 26 Rotation stopper, 28 Case, 40 Linear output mechanism, 42 Pinion gear, 44 Connecting bolt, 46 Bearing, 48 Rack gear, 52 Protective cover, 54 Guide hole, 60 Gripper claw, 62 Linear motion part, 70 Connecting part, 72 Locking groove, 100 Robot, 110 Workpiece.

Claims

1. an air cylinder having a piston rod that moves linearly back and forth; a rotation output mechanism that includes a threaded shaft fixed to the piston rod and a nut screwed onto the threaded shaft, and converts the linear motion of the piston rod into rotational motion; a plurality of linear motion units that move forward and backward in synchronization with each other, and each of which has a gripper claw connected thereto; a linear output mechanism that converts the rotational motion output from the rotational output mechanism into linear motion and transmits the linear motion to the plurality of linear motion units, the linear output mechanism having a pinion gear that rotates in synchronization with the nut and a rack gear that meshes with the pinion gear; the nut is disposed on an inner diameter side of the pinion gear, The linear stroke of the linear motion portion is greater than the linear stroke of the piston rod, an axial extent of the nut overlaps with at least a portion of an axial extent of the pinion gear; A gripper device characterized by:

2. 2. The gripper device according to claim 1, A gripper device, characterized in that (π m z / R) > 1 is satisfied, where m is a module of the pinion gear, z is the number of teeth of the pinion gear, and R is a lead of the screw shaft.

3. 3. The gripper device according to claim 1 or 2, an axial direction of the piston rod, an axial direction of the screw shaft, an axial direction of the nut, and a rotational axis direction of the pinion gear are parallel to each other, an axial direction of the piston rod is perpendicular to the linear movement directions of the linear motion portions, an axial range of the piston rod overlaps with at least a portion of an axial range of the screw shaft; An axial range of the screw shaft overlaps with at least a portion of an axial range of the pinion gear. A gripper device comprising:

Images