VACUUM GRIPPING APPARATUS

• US 20100135760A1
• Filed: 04/25/2008
• Published: 06/03/2010
• Est. Priority Date: 04/26/2007
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Pace Innovations, L.C.
• Inventors: Hjornet, Preben
• Granted Patent: US 8,290,624 B2
• Time in Patent Office: Days
• US Class Current: 414/744.800
• CPC Class Codes: B25J 15/0616 with vacuum
• CPC Class Codes: B65B 35/18 by suction-operated grippers
• CPC Class Codes: B65G 47/917 control arrangements

Abstract

A gripper grasps irregular and deformable work pieces so as to lift and hold packaged, processed, or raw, and manipulate the work pieces for the purpose of material handling, assembly, packaging, and other robotic and automated manipulative functions. A vacuum is induced at multiple points through a flexible gripping hood to provide lifting force to, and facilitate rapid movement of, work pieces. An array of lighting devices and a double ring array of segmented mirrors provide uniform illumination to ensure accurate positioning of the gripping hood with respect to the work piece to be manipulated.

Claims

1. A vacuum gripping apparatus suited to grasp and release irregular objects, the apparatus comprising:

a gripper comprising;

a unitary flexible gripping hood that includes a base formed about a first central orifice and having a circumference of a predetermined shape surrounded by a lip that extends around the circumference of the base and extends downwardly to a circumferential rim according to a generally cosine-shaped curve that produces a predetermined deformation profile, a plurality of channels being formed into the hood, each channel passing radially outwardly from the first central orifice and down the lip to a predetermined distance from the rim, the lip being sufficiently flexible that the lip and rim are adaptable to conform to an irregularly shaped work-piece when a pressure differential between the hood and the work-piece is created, each of the channels being separated from adjacent channels by a protuberance;

a lip base mounted to the base of the hood and having a second central orifice;

a vacuum line passing through the first and second central orifices; and

a plurality of flexible hollow tubular vacuum channel fingers each having a proximal and a distal end, each finger being affixed to the gripping hood by mounting in a respective one of the channels;

a robotic arm having a tool center point to which the gripper is connected, the robotic arm controllable by a real-time computerized controller incorporating tactile and visual feedback to position the gripper adjacent the work-piece to be gripped;

at least one vacuum hose having a first and a second end, the first end in communication with the proximal ends of the fingers through the first and second orifices, the second end connected to a vacuum source and adapted to provide a suction force inside the gripping hood proximate the first central orifice and to provide a suction force through the vacuum hose to the distal ends of the fingers thereby enabling suction gripping at a plurality of points proximate the rim of the gripping hood, whereby upon initial application of a suction the majority of the vacuum force is applied through the first orifice, causing portions of the work-piece to move toward the first orifice, whereupon the vacuum force is directed through the fingers, thereby causing the hood to deform about, and conform to, a surface of the work-piece;

an electronically operated high speed and high vacuum flow valve to control the level of suction in the vacuum hose;

an optical system to provide robotic arm position information, the optical system comprising;

a plurality of light emitting diodes to illuminate the work-piece;

a plurality of segmented rings of mirrors that reflect light from the light emitting diodes to provide homogeneous illumination of the work-piece;

a camera having an objective lens for recording predetermined image information of the work-piece;

memory to store images captured by the camera;

wherein the light emitting diodes illuminate the work-piece through the mirrors to permit the camera to take an image of the work-piece, following which geometric features of the irregular work-piece are extracted from the image and compared to a predefined geometrical model having similar features and a predetermined gripping offset position, whereby the robotic arm is oriented generally to align the gripper with respect to the predetermined offset position; and

a sensor to signal to the controller that a safe holding force has been achieved by the suction force and furthermore to monitor the holding force and to respond if the holding force falls below a predetermined level.

2. The apparatus of claim 1 further comprising a bottom plate connected to the lip base and floating inside the circumference of the hood.

3. The apparatus of claim 1 further comprising an obstacle formed into the lip base to prevent loose portions of the work-piece from filling the first orifice.

4. The apparatus of claim 1 further comprising a real-time computerized controller for the robotic arm that incorporates feedback to position the gripper adjacent the work-piece to be gripped.

5. The apparatus of claim 1 further comprising a swivel adaptor mounted between the robotic arm and the gripper to enable rotation of the gripper about a predetermined axis without rotation of the vacuum hose.

6. The apparatus of claim 1 further comprising a valve to control the level of vacuum force in the vacuum hose.

7. The apparatus of claim 1 in which the light emitting diodes have a spectra of predetermined wavelengths.

8. A vacuum gripping apparatus comprising:

a gripper having;

a flexible gripping hood that includes a base formed about a first central orifice and has a predetermined circumference surrounded by a flexible lip that extends around the circumference of the base and extends downwardly to a circumferential rim, a plurality of channels passing radially outwardly from the first central orifice and down the lip to a predetermined distance from the rim, the lip and rim adaptable to conform to a work-piece when a pressure differential between the hood and the work-piece is created;

a lip base mounted to the base of the hood and having a second central orifice;

a vacuum line passing through the first and second central orifices; and

a plurality of channel fingers each having a proximal and a distal end, each finger being affixed to the gripping hood by mounting in a respective one of the channels;

a robotic arm having a tool center point to which the gripper is connected; and

at least one vacuum hose in communication with the proximal ends of the fingers through the first and second orifices and connected to a vacuum source and adapted to provide a suction force inside the gripping hood proximate the first central orifice and to provide a suction force through the vacuum hose to the distal ends of the fingers thereby enabling suction gripping at a plurality of points proximate the rim of the gripping hood, whereby upon application, a vacuum force is initially applied through the first orifice, causing portions of the work-piece to move toward the first orifice, after which the vacuum force is directed along the fingers, thereby causing the hood to deform about, and conform to, a surface of the work-piece.

9. The apparatus of claim 8 wherein the hood extends downwardly to a circumferential rim according to a generally cosine-shaped curve that produces a predetermined deformation profile.

10. The apparatus of claim 8 wherein each of the channels is separated from adjacent channels by a protuberance.

11. The apparatus of claim 8 wherein the fingers are integrally molded into the hood channels.

12. The apparatus of claim 8 further comprising a bottom plate connected to the lip base and floating inside the circumference of the hood.

13. The apparatus of claim 8 further comprising an obstacle formed into the lip base to prevent loose portions of the work-piece from filling the first orifice.

14. The apparatus of claim 8 further comprising a real-time computerized controller for the robotic arm that incorporates feedback to position the gripper adjacent the work-piece to be gripped.

15. The apparatus of claim 8 further comprising a swivel adaptor mounted between the robotic arm and the gripper to enable rotation of the gripper about a predetermined axis without rotation of the vacuum hose.

16. The apparatus of claim 8 further comprising a sensor to monitor the vacuum force and to respond if the holding force falls below a predetermined level.

17. The apparatus of claim 8 further comprising a valve to control the level of vacuum force in the vacuum hose.

18. The apparatus of claim 8 further comprising an optical system comprising:

a light source to illuminate the work-piece;

at least one segmented ring of mirrors to reflect light from the light source and to illuminate the work-piece; and

a camera having an objective lens for recording predetermined image information of the work-piece.

19. The apparatus of claim 18 in which the mirrors form a static array of concentric mirrors.

20. The apparatus of claim 18 in which the light is reflected by the mirrors to strike the work-piece at steep angle to avoid reflections and maximize contrast.

21. The apparatus of claim 18 wherein the light source illuminates the work-piece to permit the camera to take an image of the work-piece, following which geometric features of the work-piece are extracted from the image and compared to a predefined geometrical model having similar features and a predetermined gripping offset position, whereby the robotic arm is oriented generally to align the gripper with respect to the predetermined offset position.

22. An optical system to provide robotic arm position information comprising:

a light source to illuminate a work-piece;

at least one segmented ring of mirrors to reflect light from the light source and thereby to illuminate the work-piece; and

a camera having an objective lens for recording predetermined image information of the work-piece.

23. The apparatus of claim 22 wherein the light source is a plurality of light emitting diodes.

24. The apparatus of claim 22 in which the light source has a spectra of predetermined wavelengths.

25. The apparatus of claim 22 in which the mirrors are resistant to breakage or corrosion.

26. The apparatus of claim 22 further comprising memory to store images captured by the camera.

27. The apparatus of claim 22 wherein the light source illuminates the work-piece through the mirrors to permit the camera to take an image of the work-piece, following which geometric features of the irregular work-piece are extracted from the image and compared to a predefined geometrical model having similar features and a predetermined gripping offset position, whereby a robotic arm may be oriented to align the gripper with respect to a predetermined offset position.