Clamping device

Abstract

A clamping device (10) includes: a plurality of clamping jaws (12); a plurality of linear motion units (30), each of the plurality of linear motion units (30) being provided on a corresponding one of the plurality of clamping jaws (12); a synchronization mechanism (32) configured to synchronize the movements of the plurality of linear motion units (30); a first cylinder (14) configured to apply its driving force to the linear motion unit or the synchronization mechanism; a second cylinder (16) having a shorter stroke and a greater driving force than the first cylinder (14); and a transmission mechanism (34) having a clutch configured to establish or release a mechanical connection between the second cylinder (16) and the synchronization mechanism (32).

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to Japanese Patent Application No. 2020 - 098561, filed on June 5, 2020, the entire content of which is incorporated herein by reference, including the specification, claims, drawings, and abstract. Technical field

[0003] The present disclosure discloses a hydraulically or pneumatically actuated gripper device. Background art

[0004] Conventionally, a gripper device is generally known as a device for gripping an object. The gripper device has a plurality of gripper jaws that approach or separate from each other to thereby grip or release the object. Such a gripper device is typically used as, for example, an end - effector of a robot.

[0005] As one of the gripper devices, a hydraulically or pneumatically driven gripper device (for example, see JP H07 - 96484A) is known. In this device, the gripper jaws advance or retract by a hydraulically or pneumatically actuated cylinder.

[0006] Prior art documents:

[0007] Patent document 1: JP H07 - 96484A;

[0008] Patent document 2: JP 2019 - 76973A.

[0009] Generally, a gripper device is expected to hold heavy objects with different sizes. To achieve this, it is desirable that both the gripping force and the stroke of the gripper device are large. For a gripper device incorporating a hydraulic cylinder or a pneumatic cylinder as its drive source, the stroke of the gripper device depends on the length of the cylinder, and the gripping force of the gripper device depends on the area of the pressure - receiving surface of the cylinder. Here, when the volume of the cylinder is constant, as the area of the pressure - receiving surface increases, the stroke decreases accordingly. In other words, for a cylinder with a constant volume, an increase in the gripping force of the gripper device results in a decrease in its stroke, and an increase in the stroke results in a decrease in the gripping force. Therefore, there is a trade - off between increasing the gripping force and increasing the stroke in a gripper device. Of course, it is possible to increase both the gripping force and the stroke by increasing the volume of the cylinder. However, in this case, the entire gripper device will increase in size and weight.

[0010] In view of these circumstances, the present disclosure discloses a gripper device in which both the gripping force and the stroke can be increased while avoiding an increase in the size of the gripper device. Summary of the invention

[0011] In one aspect of the present disclosure, a clamping device includes: a plurality of clamping jaws configured to be interlockingly movable relative to each other; a plurality of linear motion units disposed on the plurality of clamping jaws in such a manner that each of the plurality of linear motion units is associated with a corresponding one of the plurality of clamping jaws; a synchronization mechanism configured to synchronize the movements of the plurality of linear motion units; a first cylinder linearly extending and retracting by hydraulic pressure or pneumatic pressure to apply a driving force of the first cylinder to the linear motion unit or the synchronization mechanism; a second cylinder linearly extending and retracting by hydraulic pressure or pneumatic pressure, and having a shorter stroke and a larger driving force than the first cylinder; and a transmission mechanism including a clutch configured to establish and release a mechanical connection between the second cylinder and the synchronization mechanism.

[0012] In the clamping device according to the above aspect, the linear motion unit may include a linear motion body mechanically coupled to a corresponding one of the clamping jaws, and the synchronization mechanism may include at least one claw rack disposed on the linear motion body and at least one synchronization gear configured to engage the at least one claw rack.

[0013] In another aspect of the present disclosure, the transmission mechanism and the synchronization mechanism may be configured to amplify the driving force of the second cylinder and transmit the amplified driving force to the linear motion unit.

[0014] In another aspect of the present disclosure, the clutch may be a one-way clutch configured to engage the second cylinder with the synchronization mechanism to transmit the driving force of the second cylinder to the synchronization mechanism when the second cylinder is actuated to linearly move in a first direction, and to disengage the second cylinder from the synchronization mechanism when the second cylinder is actuated to linearly move in a second direction opposite to the first direction.

[0015] In the clamping device according to the above aspect, the transmission mechanism may include a cam-type one-way clutch including: an outer wheel always coupled to the second cylinder and configured to rotate by the extending or retracting movement of the second cylinder; a bag-shaped portion defined in an axial end face of the outer wheel, the bag-shaped portion having an outer peripheral surface designed to serve as a cam surface; an inner wheel always coupled to the synchronization mechanism and concentrically placed inside the outer wheel in the bag-shaped portion; a relay roller disposed between the cam surface and the inner wheel and configured to establish an engaged state in which the relay roller is in close contact with both the cam surface and the inner wheel when the outer wheel rotates in a first rotation direction, and to establish a disengaged state in which the relay roller is separated from at least one of the cam surface and the inner wheel when the outer wheel rotates in a second rotation direction opposite to the first rotation direction; and a pushing member configured to push the relay roller into the engaged state.

[0016] In another aspect of the present disclosure, the transmission mechanism may include a cam-type one-way clutch, and the cam-type one-way clutch includes: an inner wheel that is always connected to the second cylinder and is configured to rotate by the extension or retraction movement of the second cylinder; a pocket portion defined in the axial end surface of the inner wheel, and the pocket portion has an outer peripheral surface designed to serve as a cam surface; an outer wheel that is always connected to the synchronization mechanism and is placed concentrically around the inner wheel; a relay roller disposed between the cam surface and the outer wheel, and configured to establish an engagement state in which the relay roller is in close contact with both the cam surface and the outer wheel when the inner wheel rotates in the first rotation direction, and establish a disengaged state in which the relay roller is separated from at least one of the cam surface and the outer wheel when the inner wheel rotates in a second rotation direction opposite to the first rotation direction; and a propulsion member configured to push the relay roller into the engagement state.

[0017] In another aspect of the present disclosure, the transmission mechanism may include a ratchet-type one-way clutch, and the ratchet-type one-way clutch includes: a rod that is always connected to the second cylinder and is configured to swing by the extension or retraction movement of the second cylinder; a ratchet pawl connected to the rod and configured to pivot in response to the swinging movement of the rod; and a ratchet gear that is always connected to the synchronization mechanism to interlock with the synchronization mechanism, and is configured to rotate when the ratchet pawl pivots in a first pivoting direction, and not rotate when the ratchet pawl pivots in a second pivoting direction opposite to the first pivoting direction.

[0018] In another aspect of the present disclosure, the transmission mechanism may include a claw clutch, and the claw clutch includes: an output wheel that is always connected to the synchronization mechanism to interlock with the synchronization mechanism; an input wheel that is always connected to the second cylinder and is configured to rotate by the extension or retraction movement of the second cylinder, and the input wheel advances axially to engage at least a part of the output wheel in the circumferential direction of the input wheel; and an actuator configured to move the input wheel axially forward or backward.

[0019] In another aspect of the present disclosure, the plurality of clamping claws may include N clamping claws, where N ≥ 3; the N clamping claws are configured to be able to move toward or away from each other along the sides of a polygon composed of N sides; each of the linear motion units may include a linear motion body mechanically connected to a corresponding one of the N clamping claws; and the synchronization mechanism may include: a claw rack disposed on the linear motion body, where the synchronization mechanism includes N claw racks; and a first synchronization gear disposed at the center of the polygon and configured to directly or indirectly engage with all N claw racks simultaneously.

[0020] In the clamping device disclosed herein, both the clamping force and the stroke can be increased without increasing the size of the clamping device. Description of the Drawings

[0021] Embodiments of the present disclosure will be described based on the following drawings, in which:

[0022] Figure 1 is a perspective view of the clamping device as viewed from the front;

[0023] Figure 2 is a perspective view of the clamping device as viewed from the rear;

[0024] Figure 3 shows the structure of the drive system for the clamping device;

[0025] Figure 4 is a schematic view of the clamping device from which the front cover has been removed Figure 1 ;

[0026] Figure 5 is a view of the clamping device from which the rear cover has been removed Figure 2 ;

[0027] Figure 6 is a perspective view showing a part of the transmission mechanism;

[0028] Figure 7 is a front view of the transmission mechanism in which the second cylinder is fully retracted;

[0029] Figure 8 is a front view of the transmission mechanism in which the second cylinder extends from the state shown Figure 7 ;

[0030] Figure 9 is a view showing an alternative example of a cam-type one-way clutch;

[0031] Figure 10 is a perspective view of another clamping device;

[0032] Figure 11 shows the structure of the synchronization mechanism installed in the clamping device Figure 10 ;

[0033] Figure 12 is a front view of the transmission mechanism for the synchronization mechanism in Figure 11 in which the second cylinder is fully retracted;

[0034] Figure 13 is a front view of the transmission mechanism in which the second cylinder extends from the state shown Figure 12 ;

[0035] Figure 14 shows another example of the transmission mechanism;

[0036] Figure 15 is a perspective view of a clamping device equipped with multiple clamping jaws; and

[0037] Figure 16 shows the installation inFigure 15 The structure of the synchronization mechanism in the clamping device. Detailed implementation

[0038] Hereinafter, the structure of the clamping device 10 will be described with reference to the drawings. Figure 1 is a perspective view of the clamping device 10 viewed from the front, and Figure 2 is a perspective view of the clamping device 10 viewed from the back. Figure 3 shows the structure of the drive system of the clamping device 10. The clamping device 10 is designed to be used as an end effector of a robot (not shown). The clamping device 10 includes a pair of clamping jaws 12. The clamping jaws 12 are movable in a direction approaching or separating from each other, and when they move closer to each other, the clamping jaws 12 can hold an object therebetween.

[0039] The first cylinder 14 (see Figure 1 ) and the second cylinder 16 (see Figure 2 ) are installed as drive sources for the clamping jaws 12. The first cylinder 14 and the second cylinder 16 are both pneumatically actuated cylinders. When using the clamping device 10, as Figure 3 shown, the first cylinder 14 and the second cylinder 16 are respectively connected to the first cylinder drive unit 20 and the second cylinder drive unit 22. Each of the cylinder drive units 20 and 22 is configured to drive the corresponding one of the cylinders 14 and 16, and includes at least one air compressor, and may also include other components such as valves and air tanks. The actuation of the cylinder drive units 20, 22 is controlled by the controller 18. The controller 18 is a computer having a processor and a memory, and can be implemented, for example, by the controller of the robot in which the clamping device 10 is installed. It can be clearly seen from the Figure 3 shown structure that the first cylinder 14 and the second cylinder 16 can operate independently of each other.

[0040] In addition, in this example, the first cylinder 14 is a compact cylinder having a long stroke but a small driving force. On the other hand, the second cylinder 16 has a driving force greater than that of the first cylinder 14, and the stroke of the second cylinder 16 is shorter than that of the first cylinder 14. In this regard, the second cylinder 16 is also a compact cylinder with a limited stroke.

[0041] The movement of the first cylinder 14 is transmitted to each clamping jaw 12 via the linear motion units 30a and 30b and the synchronization mechanism 32, which will be explained with reference to Figure 4 below. Figure 4 Schematically shows the clamping device 10 from which the front cover 40 has been removed. As Figure 1 shown in Figure 4As shown, the linear motion units 30a and 30b are mounted on the clamping jaws 12 one by one. It should be noted that when the difference between the linear motion units 30a and 30b can be ignored, the linear motion units 30a and 30b are simply referred to as "linear motion unit 30" without using the suffix letters a or b. The same applies to the housing 44 and the linear motion body 42 to be described below.

[0042] Each linear motion unit 30 has a housing 44 and a linear motion body 42. The linear motion body 42 is an elongated cylindrical member extending along the traveling direction of the clamping jaw 12. The linear motion body 42 is mechanically coupled to a corresponding one of the clamping jaws 12, and when the linear motion body 42 linearly advances and retreats, the clamping jaw 12 linearly moves forward and backward. The two linear motion bodies 42 are arranged at approximately 180-degree rotationally symmetric positions around a synchronous gear 50 located between the linear motion bodies 42. The linear motion body 42 has an outer peripheral surface on which one or more spline grooves 46 extending in the forward and backward directions are defined. Guide protrusions (not shown) in the housing 44 to be described below are fitted into the spline grooves 46 to prevent the linear motion body 42 from rotating, thereby restricting the movable direction of the linear motion body 42.

[0043] The outer peripheral surface of the linear motion body 42 also has a claw rack 48 extending in the forward and backward directions. The claw rack 48 forms part of the synchronization mechanism 32 and is configured to engage the synchronous gear 50. One of the two linear motion bodies 42 (i.e., the linear motion body 42a) is mechanically coupled to the piston 14a of the first cylinder 14, and thus can advance or retreat when the first cylinder 14 is driven.

[0044] The housing 44 is fixed to a fixing member (e.g., the front cover 40) and held in a fixed position regardless of the forward and backward movement of the clamping jaw 12. An opening is defined somewhere between the axial ends of the housing 44 to expose the claw rack 48 of the linear motion body 42 to the synchronous gear 50. The inner circumferential surface of the housing 44 has guide protrusions (not shown) fitted into the spline grooves 46.

[0045] The synchronization mechanism 32 is configured to synchronize the movements of the two linear motion bodies 42. The synchronization mechanism 32 includes the claw racks 48 formed on the two linear motion bodies 42 and the synchronous gear 50 that engages with the claw racks 48. As Figure 4 shown, the synchronous gear 50 simultaneously engages with the two claw racks 48 respectively formed on the two linear motion units 30. By arranging the synchronous gear 50, the movements of the two linear motion bodies 42 can be synchronized.

[0046] The behavior of the clamping jaw 12 will be explained in more detail. When one of the linear motion bodies 42 (i.e., the linear motion body 42a) is in Figure 4When moving linearly downward through the extending motion of the first cylinder 14, the pawl rack 48 provided on the linear moving body 42a moves linearly downward accordingly in Figure 4 in a linear downward motion. As a result, the synchronizing gear 50 engaged with the pawl rack 48 rotates counterclockwise in Figure 4 in a counterclockwise direction. The counterclockwise rotation of the synchronizing gear 50 causes the other one in the linear moving body 42 (i.e., the linear moving body 42b) to move linearly upward in Figure 4 in a linear upward motion. In other words, when the first cylinder 14 extends, the two clamping claws 12 move in directions away from each other and thus open. When the first cylinder 14 retracts, the two clamping claws 12 act in a manner opposite to the above direction. That is, the two clamping claws 12 move toward each other and thus close.

[0047] Here, in this example, two movable units are provided, and each movable unit includes a clamping claw 12 and a linear moving body 42. The two movable units have substantially the same mass, which allows the two movable units to act as counterweights for each other. For this reason, the two clamping claws 12 and the two linear moving bodies 42 can move even when the driving force of the first cylinder 14 is small. Although the stroke of the first cylinder 14 is long, its driving force is small as described above. Therefore, the clamping device 10 incorporating only the first cylinder 14 will not have a strong enough clamping force to hold, for example, a heavy object. Considering this, a second cylinder 16 and a transmission mechanism 34 for transmitting the motion of the second cylinder 16 are installed in this example.

[0048] The second cylinder 16 is a cylinder having a shorter stroke and a larger driving force than that of the first cylinder 14. The transmission mechanism 34 transmits the action of the second cylinder 16 to the synchronizing gear 50. However, the transmission mechanism 34 is configured as a cam type one-way clutch, which is used to transmit the driving force of the second cylinder 16 being extended but does not transmit the driving force of the second cylinder 16 being retracted. Refer to Figures 5 to 8 to explain the components of the transmission mechanism 34. Figure 5 is a view showing the clamping device with the rear cover 54 removed therefrom, and Figure 2 and Figure 6 is a perspective view showing a part of the transmission mechanism 34. Figure 7 is a front view showing the transmission mechanism 34 in a state where the second cylinder 16 is fully retracted, and Figure 8 is a front view showing the transmission mechanism 34 in a state where the second cylinder 16 extends from the Figure 7 retracted state.

[0049] The transmission mechanism 34 includes a movable block 55, an outer wheel 58, an inner wheel 60, a relay roller 62, a spring plunger 70 (not shown in Figure 5 and Figure 7 but in Figure 6 and Figure 8as shown), and a fixing pin 72. The movable block 55 is always connected to the piston 16a of the second cylinder 16 so as to linearly move together with the piston 16a. The outer peripheral surface of the movable block 55 is provided with an input rack 56 extending along the traveling direction of the movable block 55.

[0050] The outer wheel 58 is a rotating member having a gear on its outer circumferential surface. The outer wheel 58 is always mechanically connected to the second cylinder 16 via the input rack 56, and thus rotates by the extending or retracting movement of the second cylinder 16. Here, in Figure 5 the example of, when the second cylinder 16 extends, the outer wheel 58 rotates in the counterclockwise direction, and when the second cylinder 16 retracts, the outer wheel 58 rotates in the clockwise direction. Hereinafter, the rotation direction of the outer wheel 58 that rotates by the extending movement of the second cylinder 16 (i.e., Figure 5 the counterclockwise direction in ) is referred to as "the first rotation direction R1", and the rotation direction of the outer wheel 58 that rotates by the retracting movement of the second cylinder 16 (i.e., Figure 5 the clockwise direction in ) is referred to as "the second rotation direction R2".

[0051] A pocket portion 64 is defined on the axial end surface of the outer wheel 58, and the pocket portion is a recessed area. The outer peripheral surface of the pocket portion 64 serves as a cam surface 66 for controlling the position of a relay roller 62 to be described below. The contour of the pocket portion 64 is substantially formed in the shape of a cross in an axial view. Therefore, the space defined by the outer circumferential surface of the inner wheel 60 and the cam surface 66 has a shape composed of four approximate rectangles arranged at 90-degree intervals. Hereinafter, the approximate rectangular space is referred to as "pocket piece 64a", and the width of the space between the cam surface 66 and the outer circumferential surface of the inner wheel 60 is referred to as "pocket width D". The cam surface 66 is inclined such that the pocket width D gradually decreases from the end in the first rotation direction R1 toward the end in the second rotation direction R2.

[0052] The inner wheel 60 and the relay roller 62 are placed inside the pocket portion 64. The inner wheel 60 is a rotating member concentrically provided inside the outer wheel 58. The inner wheel 60 is always mechanically connected to the synchronizing gear 50 via an output shaft 61. Therefore, the inner wheel 60 always rotates in synchronization with the synchronizing gear 50. As will be explained below, when the outer wheel 58 rotates along the first rotation direction R1, the inner wheel 60 is connected to the outer wheel 58 via the relay roller 62 and rotates in the same direction as the outer wheel 58 (i.e., the first rotation direction R1). When the outer wheel 58 and the inner wheel 60 rotate in the first rotation direction R1, the synchronizing gear 50 rotates in the direction of closing the clamping jaws 12 (in the Figure 4 clockwise direction in ).

[0053] The relay roller 62 is disposed between the outer circumferential surface of the inner wheel 60 and the cam surface 66. One relay roller 62 is placed in a bag-shaped piece 64a, and a total of four relay rollers 62 are arranged. Here, the bag width D of the bag-shaped piece 64a is sufficiently larger than the diameter of the relay roller 62 at the position near the end in the first rotation direction R1. Therefore, as Figure 7 shown, when the relay roller 62 is located at the end of the bag-shaped piece 64a toward the first rotation direction R1, the relay roller 62 is in a state of being separated from at least one of the cam surface 66 (and thus the outer wheel 56) or the inner wheel 60. Hereinafter, the position where the relay roller 62 is separated from at least one of the outer roller 58 and the inner wheel 60 is referred to as the "disengagement position".

[0054] On the other hand, the bag width D becomes smaller than the diameter of the relay roller 62 near the circumferential center of the bag-shaped piece 64a. Therefore, as Figure 8 shown, the relay roller 62 located at the position near the circumferential center of the bag-shaped piece 64a is in close contact with the cam surface 66 (and thus the outer wheel 58) and the inner wheel 60. Hereinafter, the position where the relay roller 62 is in close contact with the outer roller 58 and the inner wheel 60 is referred to as the "engagement position".

[0055] The spring plunger 70 is embedded in the bag-shaped piece 64a at its end toward the first rotation direction R1. The spring plunger 70 pushes the relay roller 62 in the second rotation direction R2 (i.e., toward the engagement position). In addition, a cam hole 68 is provided for each bag-shaped piece 64 in the bottom surface of each bag-shaped piece 64, and the fixing pin 72 is inserted through the cam hole 68. The fixing pin 72 is fixed to a fixing member (e.g., the rear cover 54). Since the fixing pin 72 is fixed, when the outer wheel 58 rotates, the relative positional relationship between the fixing pin 72 and the relay roller 62 changes.

[0056] Next, with reference to Figure 7 and Figure 8 explain the power transmission achieved by the transmission mechanism 34. When the second cylinder 16 is fully retracted as Figure 7 shown, each fixing pin 72 pushes the corresponding relay roller 62 against the pushing force of the spring plunger 70 in the first rotation direction R1. Then, the relay roller 62 is placed in the disengagement position and separated from at least one of the cam surface 66 and the outer circumferential surface of the inner wheel 60. Therefore, the rotation of the outer wheel 58 is not transmitted to the inner wheel 60, and vice versa. As a result, in Figure 7 this state, even when the synchronous gear 50 rotates in response to the extension or retraction movement of the first cylinder 14, the rotation of the synchronous gear 50 only causes the inner wheel 60 to rotate and has no effect on the outer wheel 58 or the movable block 55.

[0057] On the other hand, when the second cylinder 16 extends, the outer wheel 58 rotates along the first rotation direction R1. This causes the relay roller 62 to move in a direction away from the fixed pin 72. When the fixed pin 72 and the relay roller 62 are separated from each other, the relay roller 62 is pushed along the second rotation direction R2 by the driving force of the spring plunger 70. In this state, the relay roller 62 starts to rotate around the inner wheel 60 in the clockwise direction. As a result of this orbital motion, the relay roller 62 moves to the engagement position. After reaching the engagement position, due to the wedging effect, the relay roller 62 firmly comes into close contact with the inner wheel 60 and the outer wheel 58, which causes the relay roller 62 to stop rotating. Therefore, the rotation of the outer wheel 58 is transmitted to the inner wheel 60 through the relay roller 62, so that the outer wheel 58 and the inner wheel 60 rotate together along the first rotation direction R1.

[0058] That is, in this example, when the second cylinder 16 extends, a wedging effect is generated, and the rotation of the outer wheel 58 is transmitted to the inner wheel 60 via the relay roller 62. Here, the inner wheel 60 is always connected to the synchronizing gear 50. For this reason, when the second cylinder 16 extends, the driving force of the second cylinder 16 passes through the inner wheel 60, the synchronizing gear 50, and is transmitted to the pair of clamping jaws 12 through the linear motion body 42 as a force for closing the clamping jaws 12. In this way, the clamping force of the clamping jaws 12 can be increased.

[0059] On the other hand, when the second cylinder 16 retracts from Figure 8 the state shown, the outer wheel 58 rotates along the second rotation direction R2, while the relay roller 62 rotates around the inner wheel 60 in the counterclockwise direction, which is the direction of moving away from the engagement position. As a result, since the frictional resistance of the relay roller 62 against the cam surface 66 and the outer wheel 58 becomes smaller, the rotation of the outer wheel 58 is not transmitted to the inner wheel 60. In short, according to the above structure of this example, the extending motion of the second cylinder 16 is transmitted to the inner wheel 60 and thus to the clamping jaws 12, while the retracting motion of the second cylinder 16 is not transmitted to the clamping jaws 12. It should be noted that in the state where the second cylinder 16 is fully retracted, the motion of the first cylinder 14 is not transmitted to the outer wheel 58.

[0060] Next, the drive control of the clamping device 10 will be briefly described. When the clamping jaws 12 are used to hold an object, the controller 18 pre-ops the second cylinder 16 to fully retract for releasing the engagement between the second cylinder 16 and the clamping jaws 12. In this state, the controller 18 ops the first cylinder 14 to extend so as to open the clamping jaws 12. Here, since the first cylinder 14 has a small driving force but a long stroke, the clamping jaws 12 can have a long stroke.

[0061] When the object to be grasped is positioned between the clamping jaws 12, the controller 18 operates the first cylinder 14 to retract and close the clamping jaws 12. Then, when the clamping jaws 12 physically contact the object, the controller 18 stops the operation of the first cylinder 14. Immediately before or after the clamping jaws 12 contact the object, the controller 18 operates the second cylinder 16 to start extending. The outer wheel 58 rotates along the first rotation direction R1 by the extending movement of the second cylinder 16, and thus brings the relay roller 62 into contact with and engaged with both the outer wheel 58 and the inner wheel 60. As a result of the engagement, the movement of the outer wheel 58 is transmitted to the inner wheel 60 via the relay roller 62, and the movement of the inner wheel 60 is transmitted to the clamping jaws 12 via the synchronizing gear 50 and other members. Since the second cylinder 16 has a driving force greater than that of the first cylinder 14, a stronger clamping force can be obtained by transmitting the force of the second cylinder 16 to the clamping jaws 12. In addition, since the diameter of the outer wheel 58 is sufficiently larger than the pitch diameter of the synchronizing gear 50 for amplifying the rotational force of the outer wheel 58 and thus amplifying the driving force of the second cylinder 16, it is possible to amplify the driving force of the second cylinder 16 and transmit the amplified force to the synchronizing gear 50. As a result, the clamping force of the clamping device 10 can be further increased.

[0062] As can be understood from the above explanation, in this example, the clamping jaws 12 are opened and closed by the first cylinder 14 having a long stroke and a small driving force, and the force of the second cylinder 16 having a small stroke and a large driving force is transmitted to the clamping jaws 12 only when a strong clamping force is required. In this way, a clamping device 10 having both a long stroke and a strong clamping force can be obtained without using a large cylinder. In addition, since a strong clamping force can generate a strong frictional force between the object and each clamping jaw 12, the clamping device 10 can hold the object without slipping.

[0063] Although in the above explanation, the outer wheel 58 is always connected to the second cylinder 16 and the inner wheel 60 is always connected to the synchronizing mechanism 32, this connection relationship can be established conversely. For example, as Figure 9 shown, an input gear 74 axially protruding from the drawing can be formed at the center of the inner wheel 60 and can be engaged with the input rack 56. In this case, an output shaft 61 axially protruding under the drawing can be provided at the center of the outer wheel 58 and fixed to the synchronizing gear 50. In addition, in this case, as Figure 9 shown, a bag-shaped portion 64 can be defined in the inner wheel 60, and a spring plunger 70 can be embedded in the cam surface 66 of each bag-shaped portion 64.

[0064] Hereinafter, another structural example of the clamping device 10 will be explained. Figure 10 is a perspective view of the clamping device 10 in this example. In the clamping device 10 of this example, the synchronizing mechanism 32 incorporates two synchronizing gears 76 and 78 (for the synchronizing gear 76, see Figure 11, which is not shown in Figure 10 ), and the transmission mechanism 34 is implemented by a ratchet. First, the structure of the synchronization mechanism 32 will be explained. Figure 11 shows the structure of the synchronization mechanism 32 mounted on the Figure 10 holding device 10. In this example, the holding device 10 has two linear moving bodies 42a and 42b, as in the case of the holding device 10 shown in Figure 1 and Figure 2 . The linear moving body 42a directly connected to the first cylinder 14 has a rack with a pawl 48, and the other linear moving body 42b has two racks with pawls 48, which are symmetrically arranged at 180-degree positions around the central axis of the linear moving body 42b.

[0065] The synchronization mechanism 32 includes the racks with pawls 48 provided on the linear moving body 42, a first synchronization gear 76 provided between the two linear moving bodies 42a and 42b, and a second synchronization gear 78 provided on the side of the linear moving body 42b opposite to the first synchronization gear 76. The first synchronization gear 76 engages with both racks (including the rack with a pawl 48 provided on the linear moving body 42a and one of the racks with a pawl 48 provided on the linear moving body 42b) simultaneously to synchronize the movements of the two linear moving bodies 42a and 42b. At the same time, the second synchronization gear 78 engages with the other rack with a pawl 48 on the linear moving body 42b. The second synchronization gear 78 is fixed to the output shaft 61 of the transmission mechanism 34 so as to rotate together with the output shaft 61.

[0066] Next, the transmission mechanism 34 mounted on the holding device 10 in the example of Figure 10 will be explained with reference to the drawings. Figure 12 and Figure 13 show the structure of the transmission mechanism 34. The transmission mechanism 34 includes a movable block 55, a swing rod 80, a ratchet pawl 82, and a ratchet gear 84. The movable block 55 is directly and mechanically connected to the piston 16a of the second cylinder 16 so as to linearly travel with the piston 16a. A movable pin 86 projects from the outer peripheral surface of the movable block 55.

[0067] The swing rod 80 is suspended between the output shaft 61 and the movable pin 86 and is capable of swinging around the output shaft 61. In the swing rod 80, a first cam hole 90 is defined, and the movable pin 86 is inserted through the first cam hole 90. When the movable pin 86 is lifted up and down as the second cylinder 16 is actuated, the swing rod 80 swings around the output shaft 61 while being pushed by the movable pin 86.

[0068] The serrations are formed on the outer circumferential surface of the ratchet gear 84. The ratchet gear 84 is fixed to the output shaft 61 to rotate together with the output shaft 61. In addition, as described above, the second synchronizing gear 78 is also fixed to the output shaft 61. Therefore, when the ratchet gear 84 rotates, the second synchronizing gear 78 rotates accordingly, which in turn causes the linear movement of the pair of clamping jaws 12. Here, in the illustrated example, the clamping jaws 12 move toward the closed position by the clockwise rotation of the ratchet gear 84 and move toward the open position by the counterclockwise rotation of the ratchet gear 84.

[0069] The ratchet pawl 82 is attached to an appropriate position of the swing lever 80. The tip of the ratchet pawl 82 serves as a pallet 82a that can engage with the serrations of the ratchet gear 84. The ratchet pawl 82 can pivot relative to the swing lever 80 about a rotation shaft 88 provided on the swing lever 80. In addition, the ratchet pawl 82 also has a second cam hole 92 defined at a certain midpoint in the ratchet pawl 82. A fixing pin 72 fixed to a fixing member (e.g., the rear cover 54) is inserted through the second cam hole 92. The pivoting direction of the ratchet pawl 82 is defined by the contact relationship between the second cam hole 92 and the fixing pin 72.

[0070] Specifically, when the second cylinder 16 is fully retracted as Figure 12 shown, the ratchet pawl 82 is in a position and orientation where the pallet 82a is separated from the ratchet gear 84. When the second cylinder 16 starts to extend from the fully retracted position, the ratchet pawl 82 pivots in a direction gradually approaching the ratchet gear 84 until the pallet 82a engages with the teeth of the ratchet gear 84, as Figure 13 shown. After the engagement between the pallet 82a and the teeth, the further extension action of the second cylinder 16 causes the ratchet pawl 82 to pivot in such a way that the pallet 82a advances along the circumferential direction of the ratchet gear 84 and in the clockwise direction. On the other hand, when the second cylinder 16 retracts from the fully extended state, the ratchet pawl 82 pivots in the direction opposite to the above direction. Hereinafter, the direction in which the ratchet pawl 82 pivots by the extension action of the second cylinder 16 is referred to as the "first pivoting direction S1", and the direction in which the ratchet pawl 82 pivots by the retraction action of the second cylinder 16 is referred to as the "second pivoting direction S2".

[0071] Here, from Figure 13It can be seen that each tooth 98 of the ratchet gear 84 is composed of a first side surface 98a and a second side surface 98b, and the second side surface 98b is displaced from the first side surface 98a in the counterclockwise direction. The first side surface 98a is slightly inclined in the circumferential direction, while the second side surface 98b is steeply inclined in the circumferential direction. In this case, when the pallet 82a that has engaged with the tooth 98 moves in the clockwise direction, that is, when the ratchet pawl 82 pivots along the first pivoting direction S1, the pallet 82a pushes the first side surface 98a, which causes the ratchet gear 84 to move clockwise together with the pallet 82a. On the other hand, when the pallet 82a that has engaged with the tooth 98 moves in the counterclockwise direction, that is, when the ratchet pawl 82 pivots along the second pivoting direction S2, the pallet 82a slides along the surface of the slightly inclined second side surface 98b and finally climbs over the tooth 98 to disconnect the contact with the tooth 98. As a result, the pallet 82a moving in the counterclockwise direction does not cause the rotation of the ratchet gear 84 and allows the ratchet gear 84 to remain stationary. That is to say, in this example, when the ratchet pawl 82 pivots along the first pivoting direction S1, the power transmission from the ratchet pawl 82 to the ratchet gear 84 can be achieved through the ratchet pawl 82, while when the ratchet pawl 82 pivots along the second pivoting direction S2, the power transmission from the ratchet pawl 82 to the ratchet gear 84 is interrupted. In other words, according to this example, the transmission mechanism 34 serves as a ratchet type one-way clutch, which is configured to transmit the driving force of the second cylinder 16 only when the second cylinder 16 extends, and not to transmit the driving force of the second cylinder 16 when the second cylinder 16 retracts.

[0072] Next, the power transmission performed by the transmission mechanism 34 will be explained in detail. As Figure 12 shown, when the second cylinder 16 is fully retracted, the ratchet pawl 82 is located at a position away from the ratchet gear 84. Therefore, in this state, the rotation of the second synchronizing gear 78 is not transmitted to the ratchet pawl 82. As a result, in Figure 12 the state shown, even if the second synchronizing gear 78 rotates due to the forward or retraction movement of the first cylinder 14, only the ratchet gear 84 rotates, while the ratchet pawl 82 and the swing rod 80 are not affected by the rotation of the second synchronizing gear 78.

[0073] On the other hand, when the second cylinder 16 extends, the ratchet pawl 82 pivots along the first pivoting direction S1 and thus engages with the ratchet gear 84. When the second cylinder 16 further extends after the engagement, the pallet 82a of the ratchet pawl 82 moves along the circumferential direction of the ratchet gear 84 and also moves in the clockwise direction. As a result, the driving force of the second cylinder 16 is transmitted to the ratchet gear 84 through the ratchet pawl 82, and the movement of the ratchet gear 84 is transmitted to a pair of clamping jaws 12 via the second synchronizing gear 78 and other components as a force for closing the clamping jaws 12. In this way, the clamping force of the clamping jaws 12 can be enhanced. In addition, the swing radius of the swing lever 80 is sufficiently larger than the pitch circle diameter of the second synchronizing gear 78. For this reason, the swinging force of the swing lever 80 and thus the driving force of the second cylinder 16 are amplified, and the amplified force is transmitted to the second synchronizing gear 78. Therefore, the clamping force of the clamping device 10 can be further enhanced.

[0074] When the second cylinder 16 retracts from Figure 13 the state shown, since the pallet 82a of the ratchet pawl 82 moves as described above to slide away from the teeth of the ratchet gear 84, the ratchet pawl 82 pivots along the second pivoting direction S2, and the driving force of the second cylinder 16 is not transmitted to the ratchet gear 84. That is, in the configuration of this example, the extending movement of the second cylinder 16 is transmitted to the ratchet gear 84 and thus to the clamping jaws 12, while the retracting movement of the second cylinder 16 is not transmitted to the clamping jaws 12. In addition, in the state where the second cylinder 16 is fully retracted, the movement of the first cylinder 14 is not transmitted to the ratchet pawl 82. The operation control in the clamping device 10 with such a configuration in this example is the same as that of the clamping device 10 shown in Figure 1 and Figure 2 and the description related to the control will not be repeated.

[0075] It can be clearly seen from the above explanation that also in the clamping device 10 shown in Figure 10 the first cylinder 14 with a long stroke and a small driving force is used to open and close the clamping jaws 12, while the second cylinder 16 with a short stroke and a strong driving force is only used to transmit the force of the second cylinder 16 to the clamping jaws 12 when a strong clamping force is required. As a result, a clamping device 10 with both a long stroke and a strong clamping force can be achieved without using any large-sized cylinders.

[0076] Next, another configuration example of the clamping device 10 is described. Figure 14 is a perspective view of a transmission mechanism 34 used in another clamping device 10 according to another embodiment. Although the transmission mechanism 34 in the clamping device 10 of the previous example includes a one-way clutch, Figure 14The transmission mechanism 34 shown includes a claw clutch. Specifically, the transmission mechanism 34 of this example includes an actuator 100, an input wheel 102, and an output wheel 104. An output shaft 61 axially projects from the center of the output wheel 104 and is mechanically coupled to the synchronization mechanism 32. In addition, two or more engagement teeth 104a project axially from the axial end face of the output wheel 104. The engagement teeth 104a are spaced apart from each other in the circumferential direction of the output wheel 104, as Figure 14 shown.

[0077] The input wheel 102 is opposed to the output wheel 104 in the axial direction. Engagement teeth 102a corresponding to the engagement teeth 104a project from the axial end face of the input wheel 102. When the input wheel 102 approaches the output wheel 104, the engagement teeth 102a engage with the engagement teeth 104a. In other words, the input wheel 102 advances axially to engage a part of the output wheel 104 in the circumferential direction and rotates together with the output wheel 104.

[0078] In addition, a gear 102b is formed on the outer circumferential surface of the input wheel 102. The gear 102b engages with an input rack 56 (see Figure 5 ) that advances and retracts together with the second cylinder 16. Then, the engagement between the input rack 56 and the gear 102b allows the input wheel 12 to rotate in response to the forward or backward movement of the second cylinder 16.

[0079] The actuator 100 moves the input wheel 102 forward and backward in the axial direction. The actuator 100 is not limited to any specific configuration and may be a cylinder equipped with a piston 100a that can axially project and retract as Figure 14 shown. The input wheel 102 is rotatably mounted on the piston 100a via bearings and other components. When the actuator 100 causes the input wheel 102 to advance, the input wheel 102 engages with the output wheel 104 in the circumferential direction. Through this engagement, the forward or backward movement of the second cylinder 16 is transmitted to the synchronization mechanism 32 via the input wheel 102 and the output wheel 104. On the other hand, when the actuator 100 causes the input wheel 102 to retract, the engagement between the input wheel 102 and the output wheel 104 is released. After the engagement is released, the forward or retraction movement of the second cylinder 16 is no longer transmitted to the synchronization mechanism 32. It should be noted that even if the input wheel 102 moves forward or backward, the engagement between the input rack 56 and the gear 102b is not released.

[0080] In Figure 14In the operation of the clamping device 10 in the example of , the first cylinder 14 is actuated in a state where the input wheel 102 is disengaged from the output wheel 104 to close the clamping claws 12 to hold the object between the clamping claws 12. Then, when both clamping claws 12 are in contact with the object, the first cylinder 14 stops. Immediately before or after the clamping claws 12 are in contact with the object, the controller 18 operates the actuator 100 to move the input wheel 102 forward, and also operates the second cylinder 16 to extend so as to rotate the input wheel 102. In this way, the input wheel 102 approaches the output wheel 104 while rotating, so that the engaging teeth 102a and 104a engage with each other. Then, after the engagement, the extension movement of the second cylinder 16 is transmitted to the clamping claws 12 through the input wheel 102, the output wheel 104 and the synchronization mechanism 32. As a result, a strong clamping force is applied to the clamping claws 12, which can ensure that the object is firmly held by the clamping claws 12.

[0081] To release the grip on the object, the controller 18 operates the actuator 100 to retract the input wheel 102. This releases the engagement between the input wheel 102 and the output wheel 104, which in turn disengages the connection between the second cylinder 16 and the synchronization mechanism 32. In this state, the controller 18 can actuate the first cylinder 14 to open the clamping jaws 12.

[0082] It is obvious from the above explanation that Figure 14 In the transmission mechanism 34 shown, the clamping jaws 12 are opened and closed by the first cylinder 14 having a long stroke and a small driving force, and the force of the second cylinder 16 having a short stroke and a strong driving force is transmitted to the clamping jaws 12 only when a strong clamping force is required. In this way, a clamping device 10 having both a long stroke and a strong clamping force can be obtained without using any large-sized cylinders.

[0083] The above configuration is provided by way of illustration, and the essential configuration is to open and close the clamping claw 12 using the first cylinder 14 having a long stroke and a small driving force, and to transmit the force of the second cylinder 16 having a small stroke and a strong driving force to the clamping claw 12 only when a strong clamping force is required. The configuration explained in the present disclosure may be changed in a manner different from the essential configuration. For example, the first cylinder 14 located outside the linear moving body 42 in the above description may be incorporated into the inside of the linear moving body 42. With this configuration, the size of the clamping device 10 can be further minimized.

[0084] Although the example has been explained with reference to two clamping claws 12 , the number of the clamping claws 12 is not limited to two, and three or more clamping claws 12 may be installed. Figure 15 is a perspective view of a clamping device 10 equipped with a plurality of clamping jaws 12 , three clamping jaws 12 in the example shown. Figure 16 It is shown installed in Figure 15View of the structure of the synchronization mechanism 32 in the clamping device 10. With the number of clamping jaws 12 being N, the plurality of clamping jaws 12 linearly approach each other or linearly separate from each other along different sides of a polygon composed of N sides. In Figure 15 the example of Figure 16 , where the number of clamping jaws 12 is three, the three clamping jaws 12 linearly approach each other and linearly separate from each other along different sides of an equilateral polygon composed of three sides (i.e., an equilateral triangle). In addition, the clamping jaws 12 are respectively connected to the linear motion units 30, and each linear motion unit 30 has a linear motion body 42 (see

[0085] ), and a claw rack 48 forming part of the synchronization mechanism 32 is formed on the linear motion body 42.

[0086] Meanwhile, in the above description, the second cylinder 16 is configured to transmit its driving force to the clamping jaws 12 while extending, although the second cylinder 16 can also be configured in other ways. That is, the transmission mechanism 34 can be configured to transmit the driving force applied by the retraction movement of the second cylinder 16, without transmitting the driving force applied by the extension movement of the second cylinder 16. In addition, the first cylinder 14 can be connected to the synchronization gear 50 instead of the linear motion body 42. In addition, the first cylinder 14 and the second cylinder 16 have been implemented by pneumatically actuated cylinders, but hydraulic cylinders actuated by oil pressure can be used as the first cylinder 14 and the second cylinder 16. In addition, it is required that the transmission mechanism 34 has a function of disengaging power transmission, and the components and functions of the transmission mechanism 34 other than the disengaging function can be appropriately modified.

[0087] List of reference symbols

[0088] 10 Clamping device, 12 Clamping jaws, 14 First cylinder, 16 Second cylinder, 18 Controller, 20 First cylinder drive unit, 22 Second cylinder drive unit, 30 Linear motion unit, 32 Synchronization mechanism, 34 Transmission mechanism, 40 Front cover, 42 Linear motion body, 44 Outer housing, 46 Spline groove, 48 Claw rack, 50 Synchronization gear, 54 Rear cover, 55 Movable block, 56 Input rack, 58 Outer wheel, 60 Inner wheel, 61 Output shaft, 62 Relay roller, 64 Bag-like part, 66 Cam surface, 68 Cam hole, 70 Spring plunger, 72 Fixed pin, 76 First synchronization gear, 78 Second synchronization gear, 80 Swing rod, 82 Ratchet pawl, 84 Ratchet gear, 86 Movable pin, 88 Rotation shaft, 90 First cam hole, 92 Second cam hole, 94 First synchronization gear, 96 Second synchronization gear, 98 Teeth, 100 Actuator, 102 Input wheel, 104 Output wheel.

Claims

1. A clamping device, comprising: A plurality of clamping jaws configured to move interlockingly relative to each other; A plurality of linear motion units, each linear motion unit being provided on a corresponding one of the plurality of clamping jaws; A synchronization mechanism configured to synchronize the movements of the plurality of linear motion units; A first cylinder that linearly extends and retracts by hydraulic pressure or pneumatic pressure to apply the driving force of the first cylinder to the linear motion unit or the synchronization mechanism; A second cylinder that linearly extends and retracts by hydraulic pressure or pneumatic pressure, and has a shorter stroke than the first cylinder and a greater driving force than the first cylinder; And A transmission mechanism including a clutch configured to establish and release a mechanical connection between the second cylinder and the synchronization mechanism; Wherein the clutch is a one-way clutch configured to engage the second cylinder with the synchronization mechanism to transmit the driving force of the second cylinder to the synchronization mechanism when the second cylinder is actuated to linearly move in a first direction, and to disengage the second cylinder from the synchronization mechanism when the second cylinder is actuated to linearly move in a second direction opposite to the first direction.

2. The clamping device according to claim 1, wherein: Each of the plurality of linear motion units includes a linear motion body mechanically coupled to a corresponding one of the plurality of clamping jaws; And The synchronization mechanism includes: At least one claw rack provided on the linear motion body; And At least one synchronization gear configured to engage the at least one claw rack.

3. The clamping device according to claim 2, wherein: The transmission mechanism and the synchronization mechanism are configured to amplify the driving force of the second cylinder and transmit the amplified driving force to the linear motion unit.

4. The clamping device according to claim 1, wherein: The transmission mechanism includes a cam-type one-way clutch, and the cam-type one-way clutch includes: An outer wheel that is always coupled to the second cylinder and configured to rotate by the extension or retraction movement of the second cylinder; A bag-shaped portion defined in the axial end face of the outer wheel, the bag-shaped portion having an outer peripheral surface designed to serve as a cam surface; An inner wheel that is always coupled to the synchronization mechanism and is concentrically placed inside the outer wheel in the bag-shaped portion; A relay roller provided between the cam surface and the inner wheel and configured to establish an engagement state in which the relay roller is in close contact with both the cam surface and the inner wheel when the outer wheel rotates in a first rotation direction, and to establish a disengagement state in which the relay roller is separated from at least one of the cam surface and the inner wheel when the outer wheel rotates in a second rotation direction opposite to the first rotation direction; and A propulsion member configured to push the relay roller into the engagement state.

5. The clamping device according to claim 1, characterized in that, The transmission mechanism includes a cam-type one-way clutch, and the cam-type one-way clutch includes: An inner wheel that is always coupled to the second cylinder and configured to rotate by the extension or retraction movement of the second cylinder; A pocket portion defined in an axial end face of the inner wheel, the pocket portion having an outer peripheral surface designed to serve as a cam surface; An outer wheel that is always connected to the synchronization mechanism and is placed concentrically around the inner wheel; A relay roller disposed between the cam surface and the outer wheel and configured to establish an engaged state in which the relay roller is in close contact with both the cam surface and the outer wheel when the inner wheel rotates in a first rotation direction, and to establish a disengaged state in which the relay roller is separated from at least one of the cam surface and the outer wheel when the inner wheel rotates in a second rotation direction opposite to the first rotation direction; and A propulsion member configured to push the relay roller into the engaged state.

6. The clamping device according to claim 1, wherein The transmission mechanism includes a ratchet type one-way clutch, and the ratchet type one-way clutch includes: A rod that is always connected to the second cylinder and is configured to swing by an extending or retracting movement of the second cylinder; A ratchet pawl connected to the rod and configured to pivot in response to the swinging movement of the rod; and A ratchet gear that is always connected to the synchronization mechanism to interlock with the synchronization mechanism in motion, and is configured to rotate when the ratchet pawl pivots in a first pivoting direction and not to rotate when the ratchet pawl pivots in a second pivoting direction opposite to the first pivoting direction.

7. The clamping device according to any one of claims 1 to 6, characterized in that: The plurality of clamping claws includes N clamping claws, where N≥3; The N clamping claws are configured to be able to move towards or away from each other along the sides of a polygon composed of N sides; Each of the plurality of linear motion units includes a linear motion body mechanically connected to a corresponding one of the N clamping claws; and The synchronization mechanism includes: A claw rack disposed on the linear motion body, where the synchronization mechanism includes N claw racks; And A first synchronization gear disposed at the center of the polygon and configured to directly or indirectly engage with all N claw racks simultaneously.

Images