A little lift: Bernouli's Principle is
the basis for non-contact lifting. The device uses negative air pressure
to lift objects under the effector without physical contact.
Remember the old science class trick of suspending a ping pong ball in the exhaust from a vacuum cleaner?
Similarly, engineers applied Bernoulli's Principle in the design of Bosch Rexroth's Non Contact Transfer (NCT) device. The dynamic vacuum (area of lower-than-ambient pressure) formed by the continuous airflow radially outward along the underside of an aluminum puck can pick up delicate or porous and bumpy objects. Traditional vacuum suction cups physically contact objects and cannot be used effectively on articles with many perforations or rough surfaces (such as some printed circuit boards) or soft objects (such as paper, cloth, and plastic bags). And mechanical grippers may be too rough for fragile items.
The NCTs come in diameters of 20, 30, 40, and 60 mm and lift up to 0.6 kg (1.3 lb). Regarding the Guassian-shaped underside profile, "Key challenge was shaping the curve of the surface the air flows across to optimize lift," notes Phil O'Neill, standard products manager for pneumatics. The system uses the same amount of air a suction cup would—running off an oil-free air supply of 15-105 psi, he notes.
The NCT not only can be used to handle semiconductor wafers but for items like bread and cookies. O'Neill adds that by not drawing in air, as with suction cups, the system is self cleaning and crumbs from baked goods or dirty items won't cause contamination. And because the device is non-contacting, hot or cold items can be handled during manufacturing processes.
Another interesting use is in packaging. Twin NCTs facing each other can open a plastic bag for filling without having to try and grip it or move along with it on a packaging line.
CONTACT:John Bridges, Bosch Rexroth Corp. 1953 Mercer Rd., Lexington, KY 40511-1021 Tel (859) 254-8031; Fax (859) 281-3491 e-mail: email@example.com; or enter 509 at www.designnews.com/info.