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1. WO2020142158 - FLUID-OPERATED GRIPPING APPARATUS AND METHOD FOR HOLDING A WORKPIECE IN A WORKING ORIENTATION

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[ EN ]

What is claimed is:

1. A gripping apparatus for holding a workpiece in a working orientation, the gripping apparatus comprising:

fluid-operated first, second, and third actuators that are equally spaced about a perimeter of the workpiece, wherein each actuator comprises an actuator rod coupled with a moveable piston arranged to move within a cylinder having an extend chamber and a retract chamber, and is configured to be coupled to a single pressurized fluid source;

a fluid circuit configured to: (i) supply pressurized fluid to the extend chamber of each actuator during a closing stroke of the gripping apparatus, (ii) inhibit backflow of pressurized fluid from the extend chamber of each actuator toward a pressurized fluid source, (iii) maintain a same fluid pressure within the extend chamber of each actuator while the workpiece is held by the gripping apparatus, (iv) release pressurized fluid from the extend chamber of each actuator during an opening stroke of the gripping apparatus, and (v) supply pressurized fluid to the retract chamber of each actuator during the opening stroke of the gripping apparatus; and

first, second, and third end effectors pivotally coupled with the actuator rods of the first, second, and third actuators, respectively, wherein each end effector and is configured to contact a surface of the workpiece at exactly two points.

2. The gripping apparatus of claim 1, wherein the workpiece comprises at least one curved sidewall and a first end face, and wherein the gripping apparatus further comprises backstop configured to contact the first end face, the backstop being coupled with a three-degree-of-freedom rotational backstop joint.

3. The gripping apparatus of claim 1, wherein the three-degree-of-freedom rotational backstop joint comprises a ball joint.

4. The gripping apparatus of claim 1, wherein each end effector comprises a forked end portion that defines a first curved surface configured to contact the surface of the workpiece at a first point of the exactly two points, and that defines a second curved surface configured to contact the surface of the workpiece at a second point of the exactly two points.

5. The gripping apparatus of claim 4, wherein an axis of curvature of the first curved surface is arranged 120 degrees apart from an axis of curvature of the second curved surface.

6. The gripping apparatus of claim 1, wherein each end effector comprises a three-degree-of-freedom rotational joint.

7. The gripping apparatus of claim 1, wherein the fluid circuit comprises:

a first check valve configured to inhibit backflow of pressurized fluid from the extend chamber of the first actuator toward the pressurized fluid source;

a second check valve configured to inhibit backflow of pressurized fluid from the extend chamber of the second actuator toward the pressurized fluid source; and

a third check valve configured to inhibit backflow of pressurized fluid from the extend chamber of the third actuator toward the pressurized fluid source.

8. The gripping apparatus of claim 7, wherein the fluid circuit further comprises:

a first bypass valve arranged to permit pressurized fluid to bypass the first check valve and permit flow from the retract chamber of the first actuator toward a pressurized fluid return or toward a fluid vent during the opening stroke of the gripping apparatus;

a second bypass valve arranged to permit pressurized fluid to bypass the second check valve and flow from the retract chamber of the second actuator toward a pressurized fluid return or toward a fluid vent during the opening stroke of the gripping apparatus; and

a third bypass valve arranged to permit pressurized fluid to bypass the third check valve and flow from the retract chamber of the third actuator a toward pressurized fluid return or toward a fluid vent during the opening stroke of the gripping apparatus.

9. The gripping apparatus of claim 8, wherein:

the first bypass valve comprises a three port, two position, three-way valve arranged to selectively couple the extend chamber of the first actuator to either (i) the first check valve or (ii) a pressurized fluid return or a fluid vent;

the second bypass valve comprises a three port, two position, three-way valve arranged to selectively couple the extend chamber of the second actuator to either (i) the second check valve or (ii) a pressurized fluid return or a fluid vent; and

the third bypass valve comprises a three port, two position, three-way valve arranged to selectively couple the extend chamber of the third actuator to either (i) the third check valve or (ii) a pressurized fluid return or a fluid vent.

10. The gripping apparatus of claim 2, further comprising a structural mounting ring, wherein the first, second, and third fluid-operated actuators are mounted to the structural mounting ring, and at least a portion of the backstop is centrally arranged within or proximate to an opening of the structural mounting ring.

11. The gripping apparatus of claim 1, wherein the actuator rod of each actuator is configured to travel in a substantially horizontal plane.

12. The gripping apparatus of claim 1, further comprising an adjustable pressure regulator configured to maintain a selected pressure supplied by the pressurized fluid source to the fluid circuit, whereby adjustment of the selected pressure supplied by the pressurized fluid source is configured to adjust a gripping force exerted by the first, second, and third end effectors on the workpiece.

13. The gripping apparatus of claim 1, wherein the pressurized fluid comprises a liquid.

14. The gripping apparatus of claim 1, wherein the pressurized fluid comprises a gas.

15. The gripping apparatus of claim 1, wherein the fluid circuit comprises a five port, two position, four-way valve arranged between the pressurized fluid source and the first, second, and third actuators.

16. The gripping apparatus of claim 1, wherein the workpiece comprises a substantially cylindrical shape.

17. A method for gripping and holding a workpiece in a working orientation utilizing a gripping apparatus comprising fluid-operated first, second, and third actuators that are equally spaced about a perimeter of a workpiece and comprising first, second, and third end effectors coupled with the actuator rods of the first, second, and third actuators, respectively, wherein each actuator comprises (i) a cylinder having an extend chamber and a retract chamber and (ii) an actuator rod coupled with a moveable piston arranged to move within the cylinder, the method comprising:

supplying pressurized fluid from a single pressurized fluid source to the extend chamber of each of the first, second, and third actuators during a closing stroke of the gripping apparatus, while inhibiting backflow of pressurized fluid from each extend chamber toward the pressurized fluid source, to cause (i) the first end effector to contact a surface of the workpiece only at a first pair of points, (ii) the second end effector to contact the surface of the workpiece only at a second pair of points, and (iii) the third end effector to contact the surface of the workpiece only at a third pair of points;

maintaining a same pressure of pressurized fluid within the extend chamber of each actuator while the workpiece is held by the gripping apparatus;

releasing pressurized fluid from the extend chamber of each actuator during an opening stroke of the gripping apparatus; and

supplying pressurized fluid to the retract chamber of each actuator during the opening stroke of the gripping apparatus.

18. The method of claim 17, further comprising limiting vertical movement of the workpiece with a backstop configured to contact an end face of the workpiece, wherein the backstop comprises a three-degree-of-freedom rotational backstop joint.

19. The method of claim 17, further comprising lowering at least a portion of the gripping apparatus to establish contact between a pivotally mounted backstop of the gripping apparatus and an upper surface of the workpiece, prior to said supplying of pressurized fluid from the single pressurized fluid source to the extend chamber of each of the first, second, and third actuators.

20. The method of claim 17, further comprising adjusting an output pressure of an adjustable pressure regulator configured to maintain a pressure supplied by the pressurized fluid source to the fluid circuit, whereby adjustment of the selected pressure supplied by the pressurized fluid source serves to adjust a gripping force exerted by the first, second, and third end effectors on the workpiece.