Double-acting modular articulating gripper

Abstract

To provide a cost-effective gripper for automatically accommodating the shape of the workpiece and gripping the workpiece.SOLUTION: A gripper according to the present invention includes: a base; at least one middle segment pivotably connected to the base; a distal segment pivotably connected to the at least one middle segment; at least one actuator; a yoke coupled to the at least one actuator and configured to be moved in opposing directions by the at least one actuator; and at least one tendon coupled to the distal segment at two different coupling points and coupled to the yoke. The at least one middle segment and the distal segment are configured to pivot clockwise as the at least one actuator moves the yoke in a first direction and to pivot counterclockwise as the at least one actuator moves the yoke in a second direction which is opposite to the first direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] Background to the disclosure The present invention relates to gripper tools, and more particularly to self-pivoting grippers.

[0002] The present invention relates to a pivoting gripper and incorporates elements of a modular pivoting gripper previously disclosed in US Pat. No. 1,128,5617.

[0003] A gripper is generally a mechanical device with jaws that move together or separately, driven by an actuator such as an electric motor or pneumatic piston. A tool is typically fixed to the jaws, providing some degree of conformal contact between the surface of the tool and one or more surfaces of the gripped workpiece. As the jaws move the fixed tool into contact with the gripped workpiece, the jaws exert a force on the tool, which is transmitted by the tool to hold the workpiece and subsequently translate or rotate the position of the workpiece. When the workpiece is subsequently translated or rotated, or an external force is applied to the workpiece, it is often desirable for the tool to fully or partially surround the contours of the workpiece to prevent relative motion between the workpiece and the tool.

[0004] It is known in the art to construct tools with complementary contact surface contours that correspond to the contours of a workpiece to better surround a gripped workpiece. This method of surrounding typically renders the tool suitable for gripping only a single-shaped workpiece or a series of similarly shaped workpieces that share a common surface contour. Generally, if subsequent gripping of workpieces of incompatible shapes is required, the tool must be removed and replaced, resulting in an undesirable increase in downtime and an undesirable decrease in throughput in the manufacturing or material handling operation in which the gripping device is used.

[0005] The modular pivoting gripper disclosed in U.S. Pat. No. 1,128,5617 includes an internal fluid actuator that directly supplies the actuation force for the pivoting, while a tensioned elastomeric tendon acting in a direction opposite to the fluid actuator acts to restore the rotated, pivoted portion of the gripper to its unrotated position when the fluid force is removed from the actuator. This same restoring action simultaneously returns a piston within the fluid actuator to a position suitable for providing the actuation force necessary to affect the pivoting when fluid force is reapplied to the internal actuator.

[0006] Grippers that use fluid force to move the gripper's component in one direction and then use springs or stretched elastomeric strips to return the component to its original position when the fluid force is removed are commonly referred to in the fluid force industry as "single-acting," while grippers that use fluid force to move the component in two opposing motions are commonly referred to as "double-acting."

[0007] Double-acting grippers often have the advantage of being able to provide more force in both directions of motion of the gripper components than single-acting grippers. Those skilled in the art will appreciate that this increased force in both directions improves the gripping capabilities of the gripper and, in turn, improves its ability to manipulate the gripped object.

[0008] What is needed in the art is a cost-effective gripper that automatically adapts to the shape of the workpiece to grip the workpiece.

[0009] Summary of the Invention The present invention relates to a gripper configured for double-acting operation, where multiple modular grippers can be arranged together to increase the total gripping force applied to a gripped workpiece and / or to increase the locations at which the gripping force is applied.

[0010] One form of the invention relates to a gripper for gripping a workpiece, the gripper comprising: a base body, at least one intermediate segment pivotally connected to the base body, a distal segment pivotally connected to the at least one intermediate segment, at least one actuator, a yoke coupled to the at least one actuator and configured to be moved in opposing directions by the at least one actuator, and at least one tendon coupled to the distal segment at two different coupling points and coupled to the yoke, wherein the at least one intermediate segment and the distal segment are configured to rotate clockwise when the at least one actuator moves the yoke in a first direction and to rotate counterclockwise when the at least one actuator moves the yoke in a second direction opposite the first direction.

[0011] In another aspect, the invention relates to a gripper array including a plurality of parallel grippers, each of the grippers including a base, at least one intermediate segment pivotally connected to the base, a distal segment pivotally connected to the at least one intermediate segment, at least one actuator, a yoke coupled to the at least one actuator and configured for movement in opposing directions by the at least one actuator, and at least one tendon coupled to the distal segment at two different coupling points and coupled to the yoke, wherein the at least one intermediate segment and the distal segment are configured to rotate clockwise when the at least one actuator moves the yoke in a first direction and to rotate counterclockwise when the at least one actuator moves the yoke in a second direction opposite the first direction.

[0012] An advantage of the present invention is that the gripper fingers can be pivoted by the action of an actuator to encompass a large number of workpieces of different shapes.

[0013] Another advantage of the present invention is that multiple grippers can be easily arranged together to increase the total gripping force applied to the gripped workpiece and / or to increase the locations at which the gripping force is applied.

[0014] Another advantage of the present invention is that the gripper is configured for double-acting operation, which allows for greater force to be provided in both directions of motion of the gripper components.

[0015] The above and other features and advantages of the present invention, as well as the manner in which they are achieved, will become more apparent and can be better understood by referring to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a perspective view of an embodiment of a gripper provided by the present invention; [Figure 2] FIG. 2 is an exploded view of the gripper of FIG. 1. [Figure 3] FIG. 2 is a front view of the gripper of FIG. 1. [Figure 4] FIG. 4 is a cross-sectional view of the gripper taken along line 4-4 of FIG. 3. [Figure 5] 5 is a cross-sectional view of the gripper taken along line 5-5 of FIG. 3. [Figure 6] 10 is a cross-sectional view of another embodiment of a gripper provided by the present invention, which includes two tendons instead of a single tendon. [Figure 7] 1 is a perspective view of a gripper array comprising a plurality of grippers provided by the present invention;

[0017] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set forth herein illustrate embodiments of the present invention, and such exemplifications should not be construed as limiting the scope of the invention in any way.

[0018] Detailed Description of the Invention Referring to the drawings, and more particularly to FIGS. 1-5, an exemplary embodiment of a gripper 300 is shown that includes a base 301 having attached thereto at least one intermediate segment 310, depicted as a series of identical pivoted segments 310, coupled to and covered by a pivoted distal segment 320. The gripper 300 includes at least one tendon 302 coupled to a yoke 303. The tendon 302 is coupled to the distal segment 320 at two different attachment points. The tendon 302 may include a first end of an adductor portion 317 of the tendon connected to the distal segment 320 at a first attachment point and an opposing second end of an abductor portion 318 of the tendon connected to the distal segment 320 at a second attachment point different from the first attachment point (see FIGS. 2 and 4). The tendon 302 may be in the form of a cable, for example, and may be wrapped around a tendon pulley 336. Of course, while tendon 302 is described and illustrated in accordance with the present invention as having both ends attached to distal segment 320, this is optional, and other portions of tendon 302 may be attached to distal segment 320. Set screw 304 can mechanically secure the yoke attachment point, which may be part of midsection 319 of tendon 302, to yoke 303. Midsection 319 is between the two opposing ends of tendon 302. However, in addition to or instead of such mechanical attachment, tendon 302 may be attached to yoke 303 by applying a suitable adhesive between tendon 302 and yoke 303. Tendon 302 may be constructed of any desired material. In one embodiment, tendon 302 is a polymer cable, which offers advantages over conventional steel cables, including improved fatigue and corrosion resistance, greater flexibility, improved mechanical shock distribution, and lower cost.

[0019] Pulley 305, supported by pivot pin 306 press-fit into a complementary hole in body 301 along an adducted portion 317 of tendon 302, guides the movement of tendon 302 so that as intermediate portion 319 of tendon 302 is pulled downward in the direction of arrow 85 by movement of yoke 303 relative to body 301, tendon 302 is drawn through the central passage of pivoted segment 310. While pulley 305 is shown supported directly by pivot pin 306, it will be appreciated that if pulley 305 is large enough and possible, a suitable commercially available bearing bushing, radial ball bearing, or needle bearing may be interposed between pulley 305 and pin 306.

[0020] Pivot pin 307 passes through complementary holes in base 301 and segments 310, 320, attaching one or more intermediate segments 310 to base 301, each other (if appropriate), and distal segments 320, forming a series of pinned, pivoted segments extending radially outward from base 301. While segments 310 and 320 are shown as being directly supported by pivot pin 307, it will be appreciated that where the segments are sufficiently large and possible, suitable commercially available bearing bushings, radial ball bearings, or needle bearings may be interposed between pin 307 and the pivot holes in segments 310, 320.

[0021] A first end of the adductor portion 317 of the tendon 302 can be mechanically secured to the distal segment 320 using a set screw 308. Of course, such mechanical attachment can also be achieved by applying a suitable adhesive between the tendon 302 and the segment 320. The tendons 302 pass over pulleys 309 located within each of the same segments 310. Thus, the tendons 302 properly attached between the yoke 303 and the distal segment 320 effectively form taut adductor tendons 302 located on one side of the segment pivot pin 307. While the pulley 309 is shown as being directly supported by the pivot pin 306, which is press-fit into a complementary hole in the segment 310, it should be understood that if the pulley 309 is large enough and possible, a suitable commercially available bearing bushing, radial ball bearing, or needle bearing could be interposed between the pulley and the pin.

[0022] The gripper 300 can include an abductor portion 318 of a tendon 302. The same tendon 302 that forms the adductor portion 317 of the tendon 302 can effectively form the abductor portion 318 of the tendon 302, with the abductor portion 318 of the tendon 302 located on the opposite side of the pivot pin 307. The abductor portion 318 of the tendon 302 can be covered by a protective strip 311. The outer strip 311 can be constructed of a suitable elastomeric material. The distal end of the strip 311 is attached to a complementary groove in the distal segment 320 in any desired manner, such as by a set screw 312 or by thermal or adhesive bonding. The proximal end of the elastomeric strip 311 is positioned in a complementary slot in the body 301 and is attached to the body 301 by the clamping action of a set screw 313 or other suitable thermal or adhesive bonding. The portion of the strip 311 between the attached distal end and the attached proximal end is unrestricted and is free to stretch or relax.

[0023] The abductor portion 318 of the tendon 302 extends downward from the intermediate portion 319 to the yoke 303 and around the tendon pulley 336, supported by a pivot pin 337 located in a complementary slot in the body 301, to guide the movement of the tendon 302 so that as the intermediate portion 319 of the tendon 302 is pulled upward in the direction of arrow 87 by movement of the yoke 303 relative to the body 301, the tendon 302 is retracted through a passage along the left side of the pivoted segment 310 (see FIGS. 4 and 5). While the tendon pulley 336 is shown as being supported directly by the pivot pin 337, it should be understood that if the size of the tendon pulley 336 is large enough and possible, a suitable commercially available bearing bushing, radial ball bearing, or needle bearing could be interposed between the pulley and the pin.

[0024] The abductor superior end of the tendon 302 can be mechanically secured to the distal segment 320 by the tightening action of a set screw 312. Of course, such mechanical attachment can also be achieved by applying a suitable adhesive between the tendon 302 and the segment 320. The tendons 302 pass over pulleys 335 located within each of the same segments 310. Thus, the tendons 302 properly attached between the yoke 303 and the distal segment 320 effectively form taut abductor tendons 302 located on one side of the segment pivot pin 307. While the pulley 335 is shown supported directly by the pivot pin 307, which is press-fit into a complementary hole in the segment 310, a suitable commercially available bearing bushing, radial ball bearing, or needle bearing can be interposed between the pulley and the pin if the pulley 335 is large enough and possible.

[0025] A boss 314 protruding from the side of the common segment 310 engages complementary slots 315 in the body 301 and in the segments 310, limiting the counterclockwise (CCW) rotation angle of the segments pinned to the base 301 and each successive pinned segment in the series relative to the preceding segment (FIG. 5). Thus, limited by the action of the boss 314 in the slot 315, the segments 310, 320 cannot rotate CCW about the pivot 307 beyond a position where the segments are vertically aligned with one another.

[0026] Downward movement of adductor portion 317 of tendon 302 in the direction of arrow 85 through the central passage of segment 310 induces a clockwise (CW) torque on segments 310, 320, causing the segments to rotate CW about pivot pin 107. Simultaneously, abductor portion 318 of tendon 302, exiting yoke 303 below intermediate portion 319 between tendon 302 and yoke 303 and wrapped around tendon pulley 336, is relaxed, allowing abductor portion 318 of tendon 302 to lengthen as tendon 302 is pulled upward in the direction of arrow 86 by the continued CW rotation of segments 310 and 320.

[0027] Conversely, upward movement of adductor portion 317 of tendon 302 in the direction of arrow 87 through the central passage of segment 310 relaxes adductor portion 317 of tendon 302, allowing CCW rotation of segments 310 and 320 about pivot pin 307, while simultaneously pulling abducted portion 318 of tendon 302 downward in the direction of arrow 88 about pulley 335 and tendon pulley 336, inducing CCW torque on segments 310 and 320, thereby returning the previously CW rotating segments to their respective unrotated positions. In this regard, at least one of central segment 310 and distal segment 320 is configured to rotate clockwise when yoke 303 moves in a first direction and to rotate counterclockwise when yoke moves in a second direction opposite the first direction.

[0028] Pad 316 is suitably held in a complementary recess in segment 310. Pad 316 is constructed from a material with a high static coefficient of friction, such as a suitable elastomer or nanodiamond-impregnated metal substrate, which enhances the frictional force generated between pad 316 and any surface of the gripped workpiece that the pad may come into contact with.

[0029] Strip 339 is suitably held in a complementary recess in segment 320. Strip 339 is constructed from a material with a high coefficient of static friction, such as a suitable elastomer or nanodiamond-impregnated metal substrate, which enhances the frictional force generated between strip 339 and any surface of the gripped workpiece that strip 339 may come into contact with.

[0030] One or more fluid actuators can be used to provide actuation force to the yoke 303. A surface of the yoke 303 can bear against a complementary surface of the piston 321. The piston 321 is housed in a complementary bore in the cylinder 323, such that the piston 321 is free to translate along the longitudinal axis of the cylinder 323 but is restricted in radial movement. An elastomeric seal 322 seals the outer periphery of the piston 321 against the internal bore of the cylinder 323, preventing hydraulic fluid introduced into the cylinder 323 from leaking around the piston 321 (see FIGS. 2 and 5). The cylinder 323 can be press-fit, welded, soldered, brazed, or adhesively bonded to a complementary boss on the upper cap 325, preventing leakage of hydraulic fluid between the cylinder 323 and the cap 325. A threaded port 325 A on the front face of cap 325 allows actuating fluid to be introduced into cylinder 323 between the face of cap 325 and piston seal 322 .

[0031] Opposite ends of the cylinder 323 may be press-fit, welded, soldered, brazed, or adhesively bonded to complementary bosses on the lower cap 332 to prevent leakage of hydraulic fluid between the cylinder 323 and the cap 332. An elastomeric seal 333 is positioned in a complementary groove in the lower cap 332 to seal around the rod portion of the piston 321 and prevent hydraulic fluid introduced into the cylinder 323 from leaking between the rod portion of the piston 321 and the bore through the lower cap 332 (see FIGS. 2 and 5). A threaded port 332A on the front face of the cap 332 allows hydraulic fluid to be introduced into the cylinder 323 between the seal 333 in the lower cap 332 and the piston seal 322. The lubricant-impregnated core wire 331 applies a film of lubricant to the interior walls of the cylinder 323, reducing friction between the seal 333 and the cylinder 323 and extending the service life of the seal 333. A magnet 330 suitably glued or press-fit into a complementary hole in the piston 321 can be used to activate a magnetically sensitive sensor (not shown) to indicate the position of the piston 321 within the cylinder 323 .

[0032] A boss on the end of the rod portion of piston 321 passes through complementary holes in yoke 303 and retaining ring 334 and snaps into a complementary groove in the boss of piston 321, retaining yoke 303 to piston 321. Retained by piston 321, yoke 303 is pushed or pulled by movement of piston 321 as a result of the action of hydraulic fluid entering port 325A or port 332A. Movement of yoke 303 causes corresponding movement of tendon 302 through its attachment to yoke 303 by the tightening action of set screw 304, as described above. An actuator is thereby coupled to yoke 303 and configured to move yoke 303 in opposite directions to rotate segments 310 and 320 clockwise or counterclockwise, depending on the direction of actuation of yoke 303.

[0033] Those skilled in the art will appreciate that hydraulic fluid entering port 325A exerts a force on piston 321, causing the piston to move downward in the direction of arrow 85, which in turn moves yoke 303 downward, tensioning adductor portions 317 of tendons 302 and causing segments 310 and 320 to rotate clockwise about pinion pivot pin 307. Conversely, hydraulic fluid entering port 332A exerts a force on piston 321, causing the piston to move upward in the direction of arrow 87, which in turn moves yoke 303 upward, tensioning abductor portions 318 of tendons 302 and causing segments 310 and 320 to rotate counterclockwise about pivot pin 307.

[0034] Although the present invention discloses tendon 302 with a single continuous cable, it will be appreciated that multiple cables of similar length or suitable strips may be substituted. Furthermore, it will be appreciated that the cable or suitable strip need not be continuous, but may be separated into discrete adduction and abduction sections, each section suitably attached to yoke 303, for example, by additional set screws or adhesive.

[0035] Referring to Figure 6, an alternative embodiment of a gripper 300' is shown. Gripper 300' is generally identical to gripper 300 described above in Figures 1-5, but includes a first tendon 602A coupled to distal segment 320 and yoke 303, and a second tendon 602B coupled to distal segment 320 and yoke 303. First tendon 602A is coupled to distal segment 320 at a first attachment point, and second tendon 602B is coupled to distal segment 320 at a second attachment point different from the first attachment point. Both tendons 602A and 602B are attached to yoke 303, and as shown, tendons 602A and 602B extend from opposite sides of yoke 303. The first tendon 602A acts similarly to the adductor portion 317 of the tendon 302, and the second tendon 602B acts similarly to the abductor portion 318 of the tendon 302. In all other respects, the gripper 300' may be identical to the gripper 300 previously described in Figures 1-5 and will not be described further.

[0036] Referring to FIG. 7, an exemplary embodiment of a gripper array 700 provided by the present invention is shown. The gripper array 700 includes a plurality of parallel grippers 300, as shown in FIGS. 1-5. Of course, the gripper array 700 may include one or more grippers 300′, as shown in FIG. 6. Each of the grippers 300 may include a fluid-powered linear actuator with a first port 325A and a second port 332A, and as described above, each yoke 303 moves in a corresponding direction, causing the segments 310 and 320 to rotate clockwise or counterclockwise. The gripper array 700 may further include a first fluid passage 701 fluidly connected to the first port 325A of each gripper 300 and a second fluid passage 702 fluidly connected to the second port 332A of each gripper 300. By providing fluid passage 701 and fluid passage 702, gripper 300 of gripper 700 can be selectively controlled so that by flowing fluid through each of fluid passage 701 and fluid passage 702, each of segments 310, 320 all rotate simultaneously clockwise or counterclockwise.

[0037] While this invention has been described with respect to at least one embodiment, it can be further modified within the spirit and scope of this disclosure. Accordingly, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the disclosure as come within known or customary practice in the art to which the invention pertains and which fall within the limits of the appended claims.

Claims

1. A gripper for gripping a workpiece, comprising: a substrate; at least one intermediate segment pivotally connected to the base; a distal segment pivotally connected to the at least one intermediate segment; at least one actuator; a yoke coupled to the at least one actuator and configured to be moved in opposing directions by the at least one actuator; at least one tendon attached to the distal segment at two different attachment points and attached to the yoke; Equipped with the at least one intermediate segment and the distal segment are configured to rotate clockwise when the at least one actuator moves the yoke in a first direction and to rotate counterclockwise when the at least one actuator moves the yoke in a second direction opposite the first direction.

2. 2. The gripper of claim 1, wherein the at least one tendon comprises a single tendon having an adductor portion coupled to the distal segment, an abductor portion coupled to the distal segment, and a yoke attachment point coupled to the yoke.

3. 3. The gripper of claim 2, wherein the yoke connection point is part of an intermediate section between the adduction section and the eversion section.

4. The gripper of claim 2 , wherein the single tendon is internally disposed within the base, within the at least one intermediate segment, and within the distal segment.

5. The gripper of claim 2 , wherein the inverting portion comprises a first end coupled to the distal segment, and the everting portion comprises a second end coupled to the distal segment.

6. 3. The gripper of claim 2, further comprising a plurality of pulleys internally disposed within the base and within the at least one intermediate segment, each pulley of the plurality of pulleys configured to contact the adductor portion of the single tendon.

7. The gripper of claim 2 further comprising a tendon pulley disposed on the base, the abductor portion being wrapped around the tendon pulley.

8. The gripper of claim 1 , wherein the at least one actuator is configured to move the yoke linearly.

9. The gripper of claim 1 , wherein the at least one actuator is in the form of at least one fluid-powered linear actuator.

10. The gripper of claim 9 , wherein the at least one fluid-powered linear actuator includes at least one cylinder and at least one piston slidably disposed within the at least one cylinder.

11. The gripper of claim 10 , wherein the at least one fluid-powered linear actuator includes two cylinders and two pistons disposed within the cylinders, respectively.

12. The gripper of claim 10 , wherein the at least one piston comprises a rod portion coupled to the yoke, and wherein sliding of the at least one piston within the at least one cylinder causes corresponding movement of the yoke.

13. 10. The gripper of claim 9, wherein the at least one fluid-powered linear actuator comprises a first port and a second port, wherein flow of fluid into the first port causes the at least one fluid-powered linear actuator to move the yoke in the first direction, and flow of fluid into the second port causes the at least one fluid-powered linear actuator to move the yoke in the second direction.

14. The gripper of claim 1 , wherein the at least one tendon comprises a first tendon coupled to the yoke and the distal segment and a second tendon coupled to the yoke and the distal segment.

15. The gripper of claim 1 , wherein the at least one actuator is internally disposed within the base.

16. 1. A gripper array comprising: a plurality of parallel grippers, each of the grippers comprising: a substrate; at least one intermediate segment pivotally connected to the base; a distal segment pivotally connected to the at least one intermediate segment; at least one actuator; a yoke coupled to the at least one actuator and configured to be moved in opposing directions by the at least one actuator; at least one tendon attached to the distal segment at two different attachment points and attached to the yoke; Equipped with the at least one intermediate segment and the distal segment are configured to rotate clockwise when the at least one actuator moves the yoke in a first direction and to rotate counterclockwise when the at least one actuator moves the yoke in a second direction opposite the first direction.

17. The gripper array of claim 16 , wherein each of the at least one actuators comprises a fluid-powered linear actuator.

18. 18. The gripper array of claim 17, wherein each fluid-powered linear actuator has a first port and a second port, and wherein flow of fluid into the first port causes the fluid-powered linear actuator to move the yoke in the first direction, and flow of fluid into the second port causes at least one fluid-powered linear actuator to move the yoke in the second direction.

19. 20. The gripper array of claim 18, further comprising: a first fluid passage fluidly connected to the first port of each fluid-powered linear actuator; and a second fluid passage fluidly connected to the second port of each fluid-powered linear actuator.

Images