Browse Prior Art Database

Self-Aligning Robot Gripper

IP.com Disclosure Number: IPCOM000034983D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 5 page(s) / 210K

Publishing Venue

IBM

Related People

Barenboim, M: AUTHOR

Abstract

This article describes a complaint robot gripper mechanism which provides for accurate pick-up of a part as well as for accurate placement of that part at assembly. Totes deliver work in process (WIP) to various workstations via some type of material handling system, such as a conveyor. The WIP is carried inside inserts within a tote. Because of normal tolerances associated with the insert, parts are not always positioned within the insert with a high degree of accuracy. Also, parts are shifting within their insert pockets during normal conveyor transfer. This complicates accurate part placement from the insert to the part destination, onto a pallet, or directly into a workstation.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 46% of the total text.

Page 1 of 5

Self-Aligning Robot Gripper

This article describes a complaint robot gripper mechanism which provides for accurate pick-up of a part as well as for accurate placement of that part at assembly. Totes deliver work in process (WIP) to various workstations via some type of material handling system, such as a conveyor. The WIP is carried inside inserts within a tote. Because of normal tolerances associated with the insert, parts are not always positioned within the insert with a high degree of accuracy. Also, parts are shifting within their insert pockets during normal conveyor transfer. This complicates accurate part placement from the insert to the part destination, onto a pallet, or directly into a workstation. If the part has accurate locating features such as locating pins or tooling holes, the robot can be fitted with a special part-orienting

(Image Omitted)

gripper. This gripper can engage accurate locating features upon pick- up and place the part accurately at its point of destination. However, if the part has none of the locating features, or the insert is packed tightly with parts (leaving only enough room for a regular Gripper), a different type of robot end-effector is needed. An example of a difficult part to pick and place is a printed circuit (PC) card as shown in Fig. 1A. The card has two locating holes for assembly purposes. To maximize the number of cards within the insert, the cards stand in rows rather than flat. There is only enough room between the rows to allow two narrow gripper fingers to clamp either side of a card and lift it straight up out of the insert. There is not enough room between the cards for a device to engage the locating holes and accurately position the card within the grippers as illustrated in Fig. 2. Another problem with accessing the PC card locating holes during pick-up is the subsequent assembly of the card to the stator plate. Ultimately, the PC card must be riveted to the stator plate to form the subassembly shown in Fig 1B. The stator plate has two locating holes, as does the PC card, and is carried to the workstation on a work pallet. The stator plate is already positioned by two locating pins on the pallet when it arrives at the workstation. However, the card must

(Image Omitted)

be placed flat over three stand-offs on the plate and riveted. Because the PC card must be aligned to the stator plate during riveting, the card is placed over the plate so that the work pallet locating pins engage the locating holes of the card as well. Since the locating holes of the card are used at these placement and riveting operations, they are unavailable for use as orienting features at pick- up. To overcome the restrictions outlined above as well as assure a high success rate in card placement, a specially designed compliance mechanism is incorporated as an attachment to the pitch actuator of the robot shown in Fig. 3. The compliance mechanism is made up of an air cylinder, interconnecting pistons...